95ZJ_8D.PDF

ZJ IGNITION SYSTEMS 8D - 1

IGNITION SYSTEMS

CONTENTS

page page

COMPONENT IDENTIFICATION/SYSTEM DIAGNOSTICS/SERVICE PROCEDURES . . . . . . . 6
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 IGNITION SWITCH . . . . . . . . . . . . . . . . . . . . . . . 29
COMPONENT REMOVAL/INSTALLATION . . . . . . 17 SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . 32

COMPONENT IDENTIFICATION/SYSTEM OPERATION

INDEX
page page

Automatic Shutdown (ASD) Relay . . . . . . . . . . . . . . 1 Ignition Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Camshaft Position Sensor . . . . . . . . . . . . . . . . . . . . 2 Intake Manifold Air Temperature Sensor . . . . . . . . . . 5
Crankshaft Position Sensor . . . . . . . . . . . . . . . . . . . 2 Manifold Absolute Pressure (MAP) Sensor . . . . . . . . 5
Distributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Oxygen (O2S) Sensor . . . . . . . . . . . . . . . . . . . . . . . 5
Engine Coolant Temperature Sensor . . . . . . . . . . . . 4 Powertrain Control Module (PCM) . . . . . . . . . . . . . . 5
General Information . . . . . . . . . . . . . . . . . . . . . . . . 1 Throttle Position Sensor . . . . . . . . . . . . . . . . . . . . . 5

GENERAL INFORMATION IGNITION SYSTEMS
Throughout this group, references are made to par- The distributors used on 4.0L 6-cylinder and 5.2L
ticular vehicle models by alphabetical designation or V-8 engines are basically the same for the 1995
by the particular vehicle nameplate. A chart showing model year. Similarities and differences between the
a breakdown of alphabetical designations is included two distributors will be discussed.
in the Introduction group at the beginning of this A multi-port, fuel injected engine is used on all
manual. models. The ignition system is controlled by the pow-
This section of the group, Component Identifica- ertrain control module (PCM) on all engines. The
tion/System Operation, will discuss ignition system PCM was formerly referred to as the SBEC or engine
operation and will identify ignition system compo- controller.
nents. The ignition system consists of:
For diagnostic procedures and adjustments, refer to • Spark plugs
the Diagnostics/Service Procedures section of this • Ignition coil
group. • Secondary ignition cables
For removal and installation of ignition system • Distributor (contains rotor and camshaft position
components, refer to the Component Removal/Instal- sensor)
lation section of this group. • Powertrain control module (PCM)
For other useful information, refer to On-Board Di- • Crankshaft position sensor
agnostics in the General Diagnosis sections of Group
14, Fuel System in this manual. AUTOMATIC SHUTDOWN (ASD) RELAY
For operation of the DRB scan tool, refer to the ap- The automatic shutdown (ASD) relay is located in
propriate Powertrain Diagnostic Procedures service the power distribution center (PDC) near the battery
manual. (Fig. 1). As one of its functions, it will supply battery
An Ignition specifications section is included at the voltage to the ignition coil. The ground circuit for the
end of this group. A general Maintenance Schedule ASD relay is controlled by the powertrain control
(mileage intervals) for ignition related items can be module (PCM). The PCM regulates ASD relay opera-
found in Group 0, Lubrication and Maintenance. This tion by switching the ground circuit on-and-off.
schedule can also be found in the Owners Manual.

8D - 2 IGNITION SYSTEMS ZJ

When the leading edge of the pulse ring (shutter)
enters the sync signal generator, the following occurs:
The interruption of magnetic field causes the voltage
to switch high resulting in a sync signal of approxi-
mately 5 volts.
When the trailing edge of the pulse ring (shutter)
leaves the sync signal generator, the following occurs:
The change of the magnetic field causes the sync sig-
nal voltage to switch low to 0 volts.
For component testing, refer to the Diagnostics/Ser-
vice Procedures section of this group.
For removal and installation of this component, re-
fer to the Component Removal/Installation section of
this group.

CRANKSHAFT POSITION SENSOR
4.0L 6-CYLINDER ENGINES WITH MANUAL
TRANSMISSION:
The crankshaft position sensor is mounted to the
transmission bellhousing with two bolts at the left/
Fig. 1 Power Distribution Center rear side of the engine block (Fig. 3).

CAMSHAFT POSITION SENSOR
The camshaft position sensor is located in the dis-
tributor (Fig. 2) on all engines. This sensor is similar
on both the 4.0L and 5.2L engines for the 1995 model
year.

Fig. 3 Crankshaft Position Sensor—4.0L Engine
With Manual Transmission
4.0L 6-CYLINDER ENGINES WITH AUTOMATIC
TRANSMISSION
The crankshaft position sensor is mounted to the
Fig. 2 Camshaft Position Sensor—Typical transmission bellhousing with one bolt at the left/
rear side of the engine block (Fig. 4).
The camshaft position sensor contains a hall effect
device called a sync signal generator to generate a 5.2L V-8 ENGINE
fuel sync signal. This sync signal generator (Fig. 2) On 5.2L engines, the sensor is bolted to the top of
detects a rotating pulse ring (shutter) on the distrib- cylinder block near the rear of the right cylinder
utor shaft. The pulse ring rotates 180 degrees head (Fig. 5).
through the sync signal generator. Its signal is used Engine speed and crankshaft position are provided
in conjunction with the crankshaft position sensor to through the crankshaft position sensor. The sensor
differentiate between fuel injection and spark events. generates pulses that are the input sent to the pow-
It is also used to synchronize the fuel injectors with ertrain control module (PCM). The PCM interprets
their respective cylinders. the sensor input to determine the crankshaft posi-


SENSOR OPERATION—4.0L ENGINE
The flywheel/drive plate has groups of four notches
at its outer edge. On 4.0L engines there are three
sets of notches (Fig. 6).
The notches cause a pulse to be generated when
they pass under the sensor. The pulses are the input
to the PCM. For each engine revolution there are
there are 3 groups of four pulses generated on 4.0L
6-cylinder engines.
The trailing edge of the fourth notch, which causes
the pulse, is four degrees before top dead center
(TDC) of the corresponding piston.
The engine will not operate if the PCM does not re-
ceive a crankshaft position sensor input.
For removal and installation of this sensor, refer to
the Component Removal/Installation section of this
group.

With Automatic Transmission

Fig. 6 Sensor Operation—4.0L Engine—Typical
SENSOR OPERATION—5.2L V-8 ENGINE
On 5.2L engines, the flywheel/drive plate has 8 sin-
gle notches, spaced every 45 degrees, at its outer
edge (Fig. 7).
Fig. 5 Crankshaft Position Sensor—5.2L Engine—
The notches cause a pulse to be generated when
Typical
they pass under the sensor. The pulses are the input
tion. The PCM then uses this position, along with to the PCM. For each engine revolution, there are 8
other inputs, to determine injector sequence and ig- pulses generated on 5.2L V-8 engines.
nition timing. The engine will not operate if the PCM does not re-
The sensor is a hall effect device combined with an ceive a crankshaft position sensor input.
internal magnet. It is also sensitive to steel within a For component testing, refer to the Diagnostics/Ser-
certain distance from it. vice Procedures section of this group.
this group.


this group.

IGNITION COIL
Battery voltage is supplied to the ignition coil pos-
itive terminal from the ASD relay.
The powertrain control module (PCM) opens and
closes the ignition coil ground circuit for ignition coil
operation.
Base ignition timing is not adjustable. By con-
trolling the coil ground circuit, the PCM is able to set
the base timing and adjust the ignition timing ad-
vance. This is done to meet changing engine operat-
ing conditions.
The ignition coil is not oil filled. The windings are
embedded in an epoxy compound. This provides heat
and vibration resistance that allows the ignition coil
to be mounted on the engine.
On 4.0L 6-cylinder engines, the ignition coil is
mounted to a bracket on the side of the engine (Fig.
8).
Fig. 7 Sensor Operation—5.2L V-8 Engine On 5.2L V-8 engines, the ignition coil is mounted to
DISTRIBUTORS a bracket at the front of the right cylinder head (Fig.
All engines are equipped with a camshaft driven 9). This bracket is also used to mount the automatic
mechanical distributor, containing a shaft driven dis- belt tensioner.
tributor rotor. All distributors are equipped with an
internal camshaft position (fuel sync) sensor (Fig. 2).
This sensor provides fuel injection synchronization
and cylinder identification.
The distributors on 4.0L or 5.2L engines do not
have built in centrifugal or vacuum assisted advance.
Base ignition timing and all timing advance is con-
trolled by the powertrain control module (PCM). Be-
cause ignition timing is controlled by the PCM, base
ignition timing is not adjustable on any of these
engines.
On the 4.0L 6-cylinder engine, the distributor is
locked in place by a notch on the distributor housing.
The distributor holddown clamp bolt passes through
this notch when installed. Because the distributor po-
sition is locked when installed, its rotational position
can not be changed. Do not attempt to modify the Fig. 8 Ignition Coil—4.0L Engine—Typical
distributor housing to get distributor rotation.
Distributor position will have no effect on igni-
tion timing.
On the 5.2L V-8 engine, the distributor is held to
the engine in the conventional method using a hold-
down clamp and bolt. Although the distributor on this group.
the 5.2L engine can be rotated, it will have no
effect on ignition timing. ENGINE COOLANT TEMPERATURE SENSOR
All distributors contain an internal oil seal that For an operational description, diagnosis and re-
prevents oil from entering the distributor housing. moval/installation procedures, refer to Group 14,
The seal is not serviceable. Fuel System.


Fig. 9 Ignition Coil—5.2L Engine—Typical
INTAKE MANIFOLD AIR TEMPERATURE SENSOR
For an operational description, diagnosis and re-
moval/installation procedures, refer to the Diagnosis
sections of Group 14, Fuel System.
Fig. 10 PCM Location—Typical
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
moval/installation procedures, refer to Group 14, fer to the Component Removal/Installation section of
Fuel System. this group.
For diagnostics, refer to the appropriate Powertrain
POWERTRAIN CONTROL MODULE (PCM) Diagnostic Procedures service manual for operation
The PCM (formerly called the SBEC or engine con- of the DRB scan tool.
troller) is located in the right/rear side of the engine
compartment (Fig. 10). THROTTLE POSITION SENSOR
The ignition system is controlled by the PCM. For an operational description, diagnosis and re-
Base ignition timing by rotation of distributor moval/installation procedures, refer to Group 14,
is not adjustable. The PCM opens and closes the ig- Fuel System.
nition coil ground circuit to operate the ignition coil.
This is done to adjust ignition timing, both initial OXYGEN (O2S) SENSOR
(base) and advance, for changing engine operating For an operational description, diagnosis and re-
conditions. moval/installation procedures, refer to Group 14,
The amount of electronic spark advance provided Fuel System.
by the PCM is determined by five input factors: En-
gine coolant temperature, engine rpm, intake mani-
fold air temperature, manifold absolute pressure and
throttle position.


DIAGNOSTICS/SERVICE PROCEDURES

INDEX
page page

Automatic Shutdown (ASD) Relay . . . . . . . . . . . . . . 6 Ignition Timing . . . . . . . . . . . . . . . . . . . . . . . ... . 12
Camshaft Position Sensor Test . . . . . . . . . . . . . . . . 6 Intake Manifold Air Temperature Sensor Test . ... . 12
Crankshaft Position Sensor Test . . . . . . . . . . . . . . . 7 Manifold Absolute Pressure (MAP) Sensor Test .. . 12
Distributor Cap . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 On-Board Diagnostics . . . . . . . . . . . . . . . . . . ... . 16
Distributor Rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Oxygen Sensor Tests . . . . . . . . . . . . . . . . . . ... . 16
DRB Scan Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Powertrain Control Module (PCM) . . . . . . . . . ... . 12
Engine Coolant Temperature Sensor Test . . . . . . . 10 Spark Plug Secondary Cables . . . . . . . . . . . . ... . 14
General Information . . . . . . . . . . . . . . . . . . . . . . . . 6 Spark Plugs . . . . . . . . . . . . . . . . . . . . . . . . . ... . 12
Ignition Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Throttle Position Sensor Test . . . . . . . . . . . . . ... . 16
Ignition Secondary Circuit Diagnosis . . . . . . . . . . . 10

GENERAL INFORMATION
This section of the group, Diagnostics/Service Pro-
cedures, will discuss basic ignition system diagnostics
and service adjustments.
For system operation and component identification,
refer to the Component Identification/System Opera-
tion section of this group.
For removal or installation of ignition system com-
ponents, refer to the Component Removal/Installa-
For other useful information, refer to On-Board Di-
agnostics in the General Diagnosis sections of Group
14, Fuel System in this manual.
For operation of the DRB Scan Tool, refer to the
appropriate Powertrain Diagnostic Procedures ser-
vice manual.
Fig. 1 Camshaft Position Sensor—Typical
AUTOMATIC SHUTDOWN (ASD) RELAY
To perform a complete test of the ASD relay and its (1) Connect the positive (+) voltmeter lead into the
circuitry, refer to the DRB scan tool and appropriate sensor output wire. This is at done the distributor
Powertrain Diagnostics Procedures manual. To test wire harness connector. For wire identification, refer
the sensor only, refer to Relays—Operation/Testing in to Group 8W, Wiring Diagrams.
the Group 14, Fuel System section of this service (2) Connect the negative (-) voltmeter lead into the
manual. ground wire. For wire identification, refer to Group
8W, Wiring Diagrams.
CAMSHAFT POSITION SENSOR TEST (3) Set the voltmeter to the 15 Volt DC scale.
The camshaft position sensor is located in the dis- 4.0L Engines: Remove distributor cap. Rotate
tributor on all engines (Fig. 1). (crank) engine with starter until rotor is pointed in
To perform a complete test of this sensor and its the 10 o’clock position. The movable pulse ring (Fig.
circuitry, refer to the DRB scan tool. Also refer to the 1) will now be within the magnetic pickup on the
appropriate Powertrain Diagnostics Procedures man- camshaft position sensor.
ual. To test the sensor only, refer to the following: 5.2L Engines: Remove coil high-tension cable and
all spark plug cables at distributor cap. Note and
4.0L OR 5.2L ENGINE mark position of cables before removal (Fig. 2). Re-
For this test, an analog voltmeter is needed. move distributor cap from distributor (two screws).
Do not remove the distributor connector from the dis- Rotate (crank) the engine until the rotor is pointed
tributor. Using small paper clips, insert them into towards the rear of vehicle. The movable pulse ring
the backside of the distributor wire harness connec- (Fig. 1) will now be within the magnetic pickup on
tor to make contact with the terminals. Be sure that the camshaft position sensor.
the connector is not damaged when inserting the pa- (4) Turn ignition key to ON position. Voltmeter
per clips. Attach voltmeter leads to these paper clips. should read approximately 5.0 volts.


CRANKSHAFT POSITION SENSOR TEST
To perform a complete test of this sensor and its
circuitry, refer to the DRB scan tool. Also refer to the
appropriate Powertrain Diagnostics Procedures man-
ual. To test the sensor only, refer to the following:
On the 4.0L engine, the sensor is located on the
transmission bellhousing at the left/rear side of the
engine block (Figs. 3 or 4).

Fig. 2 Engine Firing Order—5.2L Engine
(5) If voltage is not present, check the voltmeter
leads for a good connection.
(6) If voltage is still not present, check for voltage
at the supply wire. For wire identification, refer to
Group 8W, Wiring Diagrams.
(7) If voltage is not present at supply wire, check
for voltage at pin-7 of powertrain control module
(PCM) 60-way connector. Leave the PCM connector
connected for this test.
(8) If voltage is still not present, perform vehicle
test using the DRB scan tool.
(9) If voltage is present at pin-7, but not at the
supply wire:
(a) Check continuity between the supply wire.
This is checked between the distributor connector
and pin-7 at the PCM. If continuity is not present,
repair the harness as necessary.
(b) Check for continuity between the camshaft
position sensor output wire and pin-44 at the PCM.
If continuity is not present, repair the harness as
necessary.
(c) Check for continuity between the ground cir-
cuit wire at the distributor connector and ground.
If continuity is not present, repair the harness as
necessary.
(10) While observing the voltmeter, crank the en-
gine with ignition switch. The voltmeter needle
should fluctuate between 0 and 5 volts while the en-
gine is cranking. This verifies that the camshaft po-
sition sensor is operating properly and a sync pulse
signal is being generated.
If a sync pulse signal is not present, replacement of Fig. 4 Crankshaft Position Sensor—4.0L Engine
the camshaft position sensor is necessary. With Automatic Transmission
For removal or installation of ignition system com-
ponents, refer to the Component Removal/Installa-
For system operation and component identification,
refer to the Component Identification/System Opera-


On the 5.2L engine, the sensor is located on the top DISTRIBUTOR CAP
of cylinder block near the rear of right cylinder head
(Fig. 5). INSPECTION
(1) Near the rear of intake manifold, disconnect Remove the distributor cap and wipe it clean with
sensor pigtail harness connector from main wiring a dry lint free cloth. Visually inspect the cap for
harness. cracks, carbon paths, broken towers, or damaged ro-
tor button (Figs. 7 and 8). Also check for white depos-
its on the inside (caused by condensation entering
the cap through cracks). Replace any cap that dis-
plays charred or eroded terminals. The inside flat
surface of a terminal end (faces toward rotor) will in-
dicate some evidence of erosion from normal opera-
tion. Examine the terminal ends for evidence of
mechanical interference with the rotor tip.

Fig. 5 Crankshaft Position Sensor—5.2L Engine—
Typical
(2) Place an ohmmeter across terminals B and C Fig. 7 Cap Inspection—External—Typical
(Fig. 6). Ohmmeter should be set to 1K-to-10K scale
for this test. The meter reading should be open (no
resistance). Replace sensor if a low resistance is indi-
cated.

Fig. 8 Cap Inspection—Internal—Typical
If replacement of the distributor cap is necessary,
transfer spark plug cables from the original cap to
Fig. 6 Crankshaft Position Sensor Connector the new cap. This should be done one cable at a time.
Each cable is installed onto the tower of the new cap
that corresponds to its tower position on the original
cap. Fully seat the cables onto the towers. If neces-
sary, refer to the Engine Firing Order diagrams
(Figs. 9 or 10).


Fig. 9 Engine Firing Order—4.0L 6-Cylinder Engine

Fig. 11 Rotor Inspection—Typical
the appropriate Powertrain Diagnostics Procedures
manual. To test the coil only, refer to the following:
The ignition coil (Figs. 12 or 13) is designed to op-
erate without an external ballast resistor.

Fig. 10 Engine Firing Order—5.2L V-8 Engine
DISTRIBUTOR ROTOR
Visually inspect the rotor (Fig. 11) for cracks, evi-
dence of corrosion, or the effects of arcing on the
metal tip. Also check for evidence of mechanical in-
terference with the cap. Some charring is normal on
the end of the metal tip. The silicone-dielectric-var-
nish-compound applied to the rotor tip for radio in-
terference noise suppression, will appear charred.
This is normal. Do not remove the charred com-
pound. Test the spring for insufficient tension. Re- Fig. 12 Ignition Coil—4.0L Engine—Typical
place a rotor that displays any of these adverse Inspect the ignition coil for arcing. Test the coil ac-
conditions. cording to coil tester manufacturer’s instructions.
Test the coil primary and secondary resistance. Re-
DRB SCAN TOOL place any coil that does not meet specifications. Refer
For operation of the DRB scan tool, refer to the ap- to the Ignition Coil Resistance chart.
propriate Powertrain Diagnostic Procedures service If the ignition coil is being replaced, the secondary
manual. spark plug cable must also be checked. Replace cable
if it has been burned or damaged.
IGNITION COIL Arcing at the tower will carbonize the cable nipple,
To perform a complete test of the ignition coil and which if it is connected to a new ignition coil, will
its circuitry, refer to the DRB scan tool. Also refer to cause the coil to fail.


Fig. 13 Ignition Coil—5.2L Engine Fig. 14 Cable Removal
If the secondary coil cable shows any signs of dam-
age, it should be replaced with a new cable and new
terminal. Carbon tracking on the old cable can cause
arcing and the failure of a new ignition coil.

ENGINE COOLANT TEMPERATURE SENSOR TEST
moval/installation procedures, refer to Group 14,
Fuel System.

IGNITION SECONDARY CIRCUIT DIAGNOSIS
CHECKING FOR SPARK

CAUTION: When disconnecting a high voltage cable
from a spark plug or from the distributor cap, twist
Fig. 15 Checking for Spark—Typical
the rubber boot slightly (1/2 turn) to break it loose
(Fig. 14). Grasp the boot (not the cable) and pull it THE PULLEYS, BELTS OR THE FAN. DO NOT WEAR
off with a steady, even force. LOOSE FITTING CLOTHING.

(1) Disconnect the ignition coil secondary cable (2) Rotate (crank) the engine with the starter mo-
from center tower of the distributor cap. Hold the ca- tor and observe the cable terminal for a steady arc. If
ble terminal approximately 12 mm (1/2 in.) from a steady arcing does not occur, inspect the secondary
good engine ground (Fig. 15). coil cable. Refer to Spark Plug Cables in this group.
Also inspect the distributor cap and rotor for cracks
WARNING: BE VERY CAREFUL WHEN THE ENGINE
IS CRANKING. DO NOT PUT YOUR HANDS NEAR
IGNITION COIL RESISTANCE


or burn marks. Repair as necessary. If steady arcing
occurs, connect ignition coil cable to the distributor
cap.
(3) Remove a cable from one spark plug.
(4) Using insulated pliers, hold the cable terminal
approximately 12 mm (1/2 in.) from the engine cylin-
der head or block while rotating the engine with the
starter motor. Observe the spark plug cable terminal
for an arc. If steady arcing occurs, it can be expected
that the ignition secondary system is operating cor-
rectly. (note that if the ignition coil cable is re-
moved for this test, instead of a spark plug
cable, the spark intensity will be much higher.)
If steady arcing occurs at the spark plug cables, but
the engine will not start, connect the DRB scan tool.
Refer to the Powertrain Diagnostic Procedures ser-
vice manual. Fig. 17 Coil Harness Connector—5.2L Engine—
Typical
FAILURE TO START TEST
To prevent unnecessary diagnostic time and wrong • If the voltage remains near zero during the entire
test results, the previous Checking For Spark test period of cranking, refer to On-Board Diagnostics in
should be performed prior to this test. Group 14, Fuel Systems. Check the powertrain con-
trol module and auto shutdown relay.
WARNING: SET PARKING BRAKE OR BLOCK THE • If voltage is at or near battery voltage and drops
DRIVE WHEELS BEFORE PROCEEDING WITH THIS to zero after 1-2 seconds of cranking, check the cam-
TEST. shaft position sensor-to-powertrain control module
circuit. Refer to On-Board Diagnostics in group 14,
(1) Unplug the ignition coil harness connector at Fuel Systems.
the coil (Figs. 16 or 17). • If voltage remains at or near battery voltage dur-
ing the entire 5 seconds, turn the key off. Remove
the 60-way connector (Fig. 18) from the powertrain
control module (PCM). Check 60-way connector for
any spread terminals.

Fig. 18 PCM 60-Way Connector
(5) Remove test lead from the coil positive termi-
Fig. 16 Coil Harness Connector—4.0L Engine— nal. Connect an 18 gauge jumper wire between the
Typical battery positive terminal and coil positive terminal.
(2) Connect a set of small jumper wires (18 gauge (6) Make the special jumper shown in figure 19.
or smaller) between the disconnected harness termi- Using the jumper, momentarily ground terminal-19
nals and the ignition coil terminals. To determine po- of the 60-way connector. A spark should be generated
larity at connector and coil, refer to the Wiring at the coil cable when the ground is removed.
Diagrams section. (7) If spark is generated, replace the powertrain
(3) Determine that sufficient battery voltage (12.4 control module (PCM).
volts) is present for the starting and ignition sys- (8) If spark is not seen, use the special jumper to
tems. ground the coil negative terminal directly.
(4) Crank the engine for 5 seconds while monitor- (9) If spark is produced, repair wiring harness for
ing the voltage at the coil positive terminal: an open condition.


Fig. 19 Special Jumper Ground-to-Coil Negative
Terminal
(10) If spark is not produced, replace the ignition
coil.

IGNITION TIMING
Base (initial) ignition timing is NOT adjust-
able on any of the 4.0L 6-cylinder or 5.2L V-8 en-
gines. Do not attempt to adjust ignition timing
by rotating the distributor.
All ignition timing functions are controlled by the
powertrain control module (PCM). Refer to On-Board Fig. 20 PCM Location—Typical
Diagnostics in the Multi-Port Fuel Injection—Gen-
eral Diagnosis section of Group 14, Fuel Systems for are pressed into the cylinder head to surround each
more information. Also refer to the appropriate Pow- spark plug cable boot and spark plug (Fig. 21). These
ertrain Diagnostics Procedures service manual for op- shields protect the spark plug boots from damage
eration of the DRB Scan Tool. (due to intense engine heat generated by the exhaust
manifolds) and should not be removed. After the
INTAKE MANIFOLD AIR TEMPERATURE SENSOR spark plug cable has been installed, the lip of the ca-
TEST ble boot should have a small air gap to the top of the
For an operational description, diagnosis and re- heat shield (Fig. 21).

TEST
Fuel System.

POWERTRAIN CONTROL MODULE (PCM)
The PCM (formerly called the SBEC or engine con-
troller) is located in the right/rear side of the engine
compartment (Fig. 20).
The ignition system is controlled by the PCM.
For diagnostics, refer to the appropriate Powertrain
Diagnostic Procedures service manual for operation
of the DRB scan tool. Fig. 21 Heat Shields—5.2L V-8 Engine
Faulty carbon and/or gas fouled plugs generally
cause hard starting, but they will clean up at higher
this group.
engine speeds. Faulty plugs can be identified in a
SPARK PLUGS number of ways: poor fuel economy, power loss, de-
For spark plug removal, cleaning, gap adjustment crease in engine speed, hard starting and, in general,
and installation, refer to the Component Removal/In- poor engine performance.
stallation section of this group. Remove the spark plugs and examine them for
5.2L V-8 Engine Only: Spark plug heat shields burned electrodes and fouled, cracked or broken por-


celain insulators. Keep plugs arranged in the order of the entire set of spark plugs may be caused by a
in which they were removed from the engine. An iso- clogged air cleaner element or repeated short operat-
lated plug displaying an abnormal condition indicates ing times (short trips).
that a problem exists in the corresponding cylinder.
Replace spark plugs at the intervals recommended in WET FOULING OR GAS FOULING
the maintenance chart in Group 0, Lubrication and A spark plug coated with excessive wet fuel or oil is
Maintenance. wet fouled. In older engines, worn piston rings, leak-
Spark plugs that have low mileage may be cleaned ing valve guide seals or excessive cylinder wear can
and reused if not otherwise defective. Refer to the cause wet fouling. In new or recently overhauled en-
following Spark Plug Condition section of this group. gines, wet fouling may occur before break-in (normal
oil control) is achieved. This condition can usually be
CONDITION resolved by cleaning and reinstalling the fouled
plugs.
NORMAL OPERATING
OIL OR ASH ENCRUSTED
The few deposits present on the spark plug will
probably be light tan or slightly gray in color. This is If one or more spark plugs are oil or oil ash en-
evident with most grades of commercial gasoline crusted (Fig. 23), evaluate engine condition for the
cause of oil entry into that particular combustion
(Fig. 22). There will not be evidence of electrode
chamber.
burning. Gap growth will not average more than ap-
proximately 0.025 mm (.001 in) per 1600 km (1000
miles) of operation. Spark plugs that have normal
wear can usually be cleaned, have the electrodes
filed, have the gap set and then be installed.

Fig. 22 Normal Operation and Cold (Carbon) Fouling
Some fuel refiners in several areas of the United Fig. 23 Oil or Ash Encrusted
States have introduced a manganese additive (MMT) ELECTRODE GAP BRIDGING
for unleaded fuel. During combustion, fuel with MMT Electrode gap bridging may be traced to loose de-
causes the entire tip of the spark plug to be coated posits in the combustion chamber. These deposits ac-
with a rust colored deposit. This rust color can be cumulate on the spark plugs during continuous stop-
misdiagnosed as being caused by coolant in the com- and-go driving. When the engine is suddenly
bustion chamber. Spark plug performance is not af- subjected to a high torque load, deposits partially liq-
fected by MMT deposits. uefy and bridge the gap between electrodes (Fig. 24).
This short circuits the electrodes. Spark plugs with
COLD FOULING/CARBON FOULING electrode gap bridging can be cleaned using standard
Cold fouling is sometimes referred to as carbon procedures.
fouling. The deposits that cause cold fouling are ba-
sically carbon (Fig. 22). A dry, black deposit on one or SCAVENGER DEPOSITS
two plugs in a set may be caused by sticking valves Fuel scavenger deposits may be either white or yel-
or defective spark plug cables. Cold (carbon) fouling low (Fig. 25). They may appear to be harmful, but
this is a normal condition caused by chemical addi-


Fig. 24 Electrode Gap Bridging Fig. 26 Chipped Electrode Insulator
tives in certain fuels. These additives are designed to has the correct heat range rating for the engine. De-
change the chemical nature of deposits and decrease termine if ignition timing is over advanced, or if
spark plug misfire tendencies. Notice that accumula- other operating conditions are causing engine over-
tion on the ground electrode and shell area may be heating. (The heat range rating refers to the operat-
heavy, but the deposits are easily removed. Spark ing temperature of a particular type spark plug.
plugs with scavenger deposits can be considered nor- Spark plugs are designed to operate within specific
mal in condition and can be cleaned using standard temperature ranges. This depends upon the thick-
procedures. ness and length of the center electrodes porcelain in-
sulator.)

Fig. 25 Scavenger Deposits
Fig. 27 Preignition Damage
CHIPPED ELECTRODE INSULATOR
A chipped electrode insulator usually results from SPARK PLUG OVERHEATING
bending the center electrode while adjusting the Overheating is indicated by a white or gray center
spark plug electrode gap. Under certain conditions, electrode insulator that also appears blistered (Fig.
severe detonation can also separate the insulator 28). The increase in electrode gap will be consider-
from the center electrode (Fig. 26). Spark plugs with ably in excess of 0.001 inch per 1000 miles of opera-
this condition must be replaced. tion. This suggests that a plug with a cooler heat
range rating should be used. Over advanced ignition
PREIGNITION DAMAGE timing, detonation and cooling system malfunctions
Preignition damage is usually caused by excessive can also cause spark plug overheating.
combustion chamber temperature. The center elec-
trode dissolves first and the ground electrode dis- SPARK PLUG SECONDARY CABLES
solves somewhat latter (Fig. 27). Insulators appear 5.2L V-8 Engine Only: Spark plug heat shields
relatively deposit free. Determine if the spark plug are pressed into the cylinder head to surround each


around the spark plug insulator. Loose cable connec-
tions can cause corrosion and increase resistance, re-
sulting in shorter cable service life.
Clean the high tension cables with a cloth moist-
ened with a nonflammable solvent and wipe dry.
Check for brittle or cracked insulation.
When testing secondary cables for damage with an
oscilloscope, follow the instructions of the equipment
manufacturer.
If an oscilloscope is not available, spark plug cables
may be tested as follows:

CAUTION: Do not leave any one spark plug cable
disconnected for longer than necessary during test-
ing. This may cause possible heat damage to the
catalytic converter. Total test time must not exceed
Fig. 28 Spark Plug Overheating ten minutes.
spark plug cable boot and spark plug (Fig. 29). These
shields protect the spark plug boots from damage With the engine not running, connect one end of a
(due to intense engine heat generated by the exhaust test probe to a good ground. Start the engine and run
manifolds) and should not be removed. After the the other end of the test probe along the entire
spark plug cable has been installed, the lip of the ca- length of all spark plug cables. If cables are cracked
ble boot should have a small air gap to the top of the or punctured, there will be a noticeable spark jump
from the damaged area to the test probe. The cable
heat shield (Fig. 29).
running from the ignition coil to the distributor cap
can be checked in the same manner. Cracked, dam-
aged or faulty cables should be replaced with resis-
tance type cable. This can be identified by the words
ELECTRONIC SUPPRESSION printed on the cable
jacket.
Use an ohmmeter to test for open circuits, exces-
sive resistance or loose terminals. Remove the dis-
tributor cap from the distributor. Do not remove
cables from cap. Remove cable from spark plug.
Connect ohmmeter to spark plug terminal end of ca-
ble and to corresponding electrode in distributor cap.
Resistance should be 250 to 1000 Ohms per inch of
cable. If not, remove cable from distributor cap tower
and connect ohmmeter to the terminal ends of cable.
If resistance is not within specifications as found in
the Spark Plug Cable Resistance chart, replace the
Fig. 29 Heat Shields—5.2L V-8 Engine cable. Test all spark plug cables in this manner.
TESTING SPARK PLUG CABLE RESISTANCE
Spark plug cables are sometimes referred to as sec-
ondary ignition cables or secondary wires. The cables
transfer electrical current from the distributor to in-
dividual spark plugs at each cylinder. The spark plug
cables are of nonmetallic construction and have a
built in resistance. The cables provide suppression of
radio frequency emissions from the ignition system.
Check the high-tension cable connections for good To test ignition coil-to-distributor cap cable, do not
contact at the ignition coil, distributor cap towers remove the cable from the cap. Connect ohmmeter to
and spark plugs. Terminals should be fully seated. rotor button (center contact) of distributor cap and
The terminals and spark plug covers should be in terminal at ignition coil end of cable. If resistance is
good condition. Terminals should fit tightly to the ig- not within specifications as found in the Spark Plug
nition coil, distributor cap and spark plugs. The Cable Resistance chart, remove the cable from the
spark plug cover (boot) of the cable should fit tight distributor cap. Connect the ohmmeter to the termi-


nal ends of the cable. If resistance is not within spec- be found in the General Diagnosis sections of
ifications as found in the Spark Plug Cable Group 14, Fuel System. For numeric flash lamp
Resistance chart, replace the cable. Inspect the igni- code charts, refer to Diagnostic Trouble Code
tion coil tower for cracks, burns or corrosion. (DTC). This can also be found in the General
For removal and installation of spark plug cables, Diagnosis sections of Group 14, Fuel System.
refer to Spark Plug Secondary Cables in the Compo-
nent Removal/Installation section.

THROTTLE POSITION SENSOR TEST
Fuel System.

OXYGEN SENSOR TESTS
For an operational description, diagnostics and re-
Fuel Systems, in this manual.

ON-BOARD DIAGNOSTICS
FOR CERTAIN IGNITION SYSTEM
COMPONENTS
The powertrain control module (PCM) performs an
On-Board Diagnostic (OBD) check for certain ignition
system components on all vehicles. This is done by
setting a diagnostic trouble code (DTC).
A DTC can be obtained in two different ways. One
of the ways is by connecting the DRB scan tool to the
data link connector. This connector is located in the Fig. 30 Data Link Connector—Typical
engine compartment (Fig. 30). Refer to the appropri-
ate Powertrain Diagnostic Procedures service manual
for operation of the DRB scan tool. The other way is
to cycle the ignition key and observe the malfunction
indicator lamp (MIL). The MIL lamp is displayed on
the instrument panel as the CHECK ENGINE lamp
(Fig. 31). This lamp will flash a numeric code. If a
numeric code number 11 (for the crankshaft position
sensor) or 42 (for the ASD relay) is observed, a prob-
lem has been found in the ignition system.
Note that the CHECK ENGINE lamp will illumi-
nate initially for approximately two seconds each
time the ignition key is turned to the ON position.
This is done for a bulb test.
For a complete operational description of all
DTC’s, for accessing a DTC and for erasing a
DTC, refer to On-Board Diagnostics. This can Fig. 31 Check Engine Lamp Location


COMPONENT REMOVAL/INSTALLATION

INDEX
page page

Automatic Shutdown (ASD Relay . . .. . . . . . . . . . . 17 Intake Manifold Air Temperature Sensor . . . . . . . . . 25
Camshaft Position Sensor . . . . . . . .. . . . . . . . . . . 17 Manifold Absolute Pressure (MAP) Sensor . . . . . . . 25
Crankshaft Position Sensor . . . . . . .. . . . . . . . . . . 18 Oxygen (O2S) Sensor . . . . . . . . . . . . . . . . . . . . . . 26
Distributors . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . 20 Powertrain Control Module (PCM) . . . . . . . . . . . . . 26
Engine Coolant Temperature Sensor . . . . . . . . . . . 20 Spark Plug Secondary Cables . . . . . . . . . . . . . . . . 28
General Information . . . . . . . . . . . .. . . . . . . . . . . 17 Spark Plugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Ignition Coil . . . . . . . . . . . . . . . . . .. . . . . . . . . . . 25 Throttle Position Sensor (TPS) . . . . . . . . . . . . . . . 28

GENERAL INFORMATION INSTALLATION
This section of the group, Component Removal/In- (1) Inspect the relay terminals in the PDC and re-
stallation, will discuss the removal and installation pair as necessary.
of ignition system components. (2) Push the relay into the connector.
For basic ignition system diagnostics and service (3) Install the relay cover.
adjustments, refer to the Diagnostics/Service Proce- (4) Connect battery cable at battery.
dures section of this group.
For system operation and component identification, CAMSHAFT POSITION SENSOR
refer to the Component Identification/System Opera- The camshaft position sensor is located in the dis-
tion section of this group. tributor (Fig. 2).

AUTOMATIC SHUTDOWN (ASD) RELAY
The ASD relay is installed in the power distribu-
tion center (PDC) (Fig. 1). Relay location is printed
on the PDC cover.

Fig. 2 Camshaft Position Sensor—Typical
REMOVAL—4.0L 6-CYLINDER ENGINE
Distributor removal is not necessary to remove
camshaft position sensor.
(1) Disconnect negative battery cable at battery.
(2) Remove distributor cap from distributor (two
screws).
(3) Disconnect camshaft position sensor wiring
harness from main engine wiring harness.
(4) Remove distributor rotor from distributor shaft.
(5) Lift the camshaft position sensor assembly
Fig. 1 Power Distribution Center
from the distributor housing (Fig. 2).
REMOVAL
(1) Disconnect negative battery cable at battery. INSTALLATION
(2) Remove the PDC cover. (1) Install camshaft position sensor to distributor.
(3) Remove the relay by lifting straight up. Align sensor into notch on distributor housing.


(2) Connect wiring harness.
(3) Install rotor.
(4) Install distributor cap. Tighten mounting
screws.
(5) Connect negative battery cable at battery.

REMOVAL—5.2L V-8 ENGINE
Distributor removal is not necessary to remove
camshaft position sensor.
(2) Remove coil high-tension cable and all spark
plug cables at distributor cap. Note and mark posi-
tion of cables (Fig. 3) before removal.

(1) Near the rear of the intake manifold, discon-
nect the pigtail harness on the sensor from the main
electrical harness.
(2) Raise and support the vehicle.
(3) Remove the two sensor mounting bolts (Fig. 4).
(4) Remove the sensor.
(5) Remove clip from sensor wire harness.

INSTALLATION
(1) Install the sensor flush against the opening in
Fig. 3 Engine Firing Order—5.2L V-8 Engine the transmission housing.
(2) Install and tighten the two sensor mounting
(3) Remove distributor cap from distributor (two bolts to 19 N⅐m (14 ft. lbs.) torque.
screws).
(4) Disconnect camshaft position sensor wiring CAUTION: The two bolts used to secure the sensor
harness from main engine wiring harness. to the transmission are specially machined to cor-
(5) Remove distributor rotor from distributor shaft. rectly space the unit to the flywheel. Do not attempt
(6) Lift the camshaft position sensor assembly to install any other bolts.
from the distributor housing (Fig. 2).
(3) Lower the vehicle.
INSTALLATION (4) Connect the electrical connector to the sensor.
(1) Install camshaft position sensor to distributor. (5) Install clip on sensor wire harness.
Align sensor into notch on distributor housing.
(2) Connect wiring harness. REMOVAL—4.0L ENGINE WITH AUTOMATIC
(3) Install rotor. TRANSMISSION
(4) Install distributor cap. Tighten mounting The crankshaft position sensor is mounted to the
screws. transmission bellhousing with a single bolt. It is lo-
(5) Install spark plug cables in correct firing order cated at the left/rear side of the engine block (Fig. 5).
(Fig. 3) to distributor cap. Be sure all spark plug ca-
The slotted adjustment hole is not used for the 1995
bles are firmly connected into distributor cap towers.
model year.
(6) Connect negative battery cable at battery.
(1) Near the rear of the intake manifold, discon-
CRANKSHAFT POSITION SENSOR nect the pigtail harness (on the sensor) from the
main electrical harness.
REMOVAL—4.0L 6-CYLINDER ENGINE WITH (2) Remove the nut holding sensor wire clip to fuel
MANUAL TRANSMISSION rail mounting stud.
The crankshaft position sensor is mounted to the (3) Remove the one sensor mounting bolt.
transmission bellhousing with two bolts at the left/ (4) Remove the sensor.
rear side of the engine block (Fig. 4). (5) Remove clip from sensor wire harness.


Fig. 6 Crankshaft Position Sensor—5.2L V-8 Engine
With Automatic Transmission
INSTALLATION
(1) Install the sensor into the access hole on the
transmission.
(2) Install sensor mounting bolt (Fig. 5).
(3) Tighten sensor mounting bolt to 6-to-8 N⅐m (50-
to-70 in. lbs.) torque.
(4) Connect the electrical connector to sensor.
(5) Install the clip to sensor wire harness.
(6) Install clip over fuel rail mounting stud. Install
clip mounting nut.

The sensor is bolted to the top of the cylinder block
near the rear of right cylinder head (Fig. 6).
(1) Remove the spark plug cable loom and spark Fig. 7 Exhaust Manifold Heat Shield—5.2L Engine
plug cables from valve cover mounting stud at rear of
right valve cover (Fig. 6). Position spark plug cables (8) Loosen EGR tube mounting nut at intake man-
to top of valve cover. ifold (Fig. 6).
(2) Remove the right exhaust manifold heat shield (9) Remove 2 EGR tube mounting bolts at exhaust
nuts/bolts and remove heat shield (Fig. 7). manifold (Fig. 6) and remove EGR tube. Discard old
(3) Disconnect 2 hoses at exhaust gas recirculation gasket at exhaust manifold.
(EGR) valve. Note position of hoses at EGR valve be- (10) Disconnect crankshaft position sensor pigtail
fore removal. harness from main wiring harness.
(4) Disconnect electrical connector and hoses at (11) Remove 2 sensor (recessed hex head) mount-
EGR valve control. Note position of hoses at valve ing bolts (Fig. 6) and remove sensor.
control before removal.
(5) Remove 2 EGR valve mounting bolts (Fig. 6) INSTALLATION—5.2L ENGINE
and remove EGR valve. Discard old EGR gasket. (1) Position crankshaft position sensor to engine
(6) Disconnect electrical connector at engine oil and install mounting bolts. Tighten bolts to 8 N⅐m
pressure sending unit. (70 in. lbs.) torque.
(7) To prevent damage to oil pressure sending unit, (2) Connect main harness electrical connector to
a special tool, such as number C-4597 must be used sensor.
(Fig. 8). Remove sending unit from engine.


DISTRIBUTORS
All distributors contain an internal oil seal that
prevents oil from entering the distributor housing.
The seal is not serviceable. The camshaft position
sensor is located in the distributor on all engines.
4.0L 6-Cylinder Engine Only: Factory replace-
ment distributors are equipped with a plastic align-
ment pin already installed. The pin is located in an
access hole on the bottom of the distributor housing
(Fig. 9). It is used to temporarily lock the rotor to the
cylinder number 1 position during installation. The
pin must be removed after installing the distributor.

Fig. 8 Oil Pressure Sending Unit—Removal/
Installation
(3) Clean the EGR tube and exhaust manifold (at
EGR tube mounting point) of any old gasket mate-
rial.
(4) Install a new gasket to exhaust manifold end of
EGR tube and install EGR tube to both manifolds.
Tighten tube mounting nut at intake manifold.
Tighten 2 mounting bolts at exhaust manifold to 23
N⅐m (204 in. lbs.) torque.
(5) Coat the threads of the oil pressure sending
unit with thread sealant. Do not allow any of the
thread sealant to get into the sending unit opening, Fig. 9 Plastic Alignment Pin—4.0L Engine
or the opening at the engine. Install sending unit to
The camshaft position sensor is located in the dis-
engine and tighten to 14 N⅐m (130 in. lbs.) torque. In-
tributor on all engines (Fig. 10). For removal/instal-
stall electrical connector to sending unit.
lation procedures, refer to Camshaft Position Sensor
(6) Clean the intake manifold and EGR valve of
in this group. Distributor removal is not necessary
any old gasket material.
for sensor removal.
(7) Install a new EGR valve gasket at intake man-
Refer to figure 11 for an exploded view of the dis-
ifold.
tributor with the 4.0L engine.
(8) Install EGR valve to intake manifold. Tighten 2
4.0L 6-Cylinder Engine Only: A fork with a slot
EGR bolts to 23 N⅐m (200 in. lbs.) torque.
is supplied on the bottom of the distributor housing
(9) Position EGR valve control and install its elec-
where the housing base seats against the engine
trical connector. Connect hoses between EGR valve
block (Fig. 11). The centerline of the slot aligns with
and EGR valve control. Connect hose between main
the distributor holddown bolt hole in the engine
engine vacuum harness and valve control.
block. Because of the fork, the distributor cannot be
(10) Install spark plug cable loom and spark plug
rotated. Distributor rotation is not necessary as all
cables to valve cover mounting stud.
ignition timing requirements are handled by the
(11) Install heat shield at right exhaust manifold.
powertrain control module (PCM). Do not attempt
to modify this fork to attain ignition timing.
ENGINE COOLANT TEMPERATURE SENSOR
All Engines: The rotational position of the distrib-
utor determines fuel synchronization only. It does not
determine ignition timing.
Fuel System.


(5) Remove the cylinder number 1 spark plug.
(6) Hold a finger over the open spark plug hole.
Rotate the engine at the vibration dampener bolt un-
til compression (pressure) is felt.
Slowly continue to rotate the engine. Do this until
the timing index mark on the vibration damper pul-
ley aligns with the top dead center (TDC) mark (0
degree) on timing degree scale (Fig. 12). Always ro-
tate the engine in direction of normal rotation. Do
not rotate the engine backward to align the timing
marks.

Fig. 10 Camshaft Position Sensor—All Engines—
Typical

Fig. 12 Align Timing Marks
(7) Remove the distributor holddown bolt and
clamp (Fig. 11).
(8) Remove the distributor from engine by slowly
lifting straight up.
Note that the rotor will rotate slightly in a counter-
clockwise direction while lifting up the distributor.
The oil pump gear will also rotate slightly in a coun-
terclockwise direction while lifting up the distributor.
This is due to the helical cut gears on the distributor
and camshaft.
Note the removed position of the rotor during dis-
tributor removal. During installation, this will be re-
Fig. 11 Distributor—4.0L Engines—Typical ferred to as the Pre-position.
REMOVAL—4.0L 6-CYLINDER ENGINE Observe the slot in the oil pump gear through the
(1) Disconnect the negative battery cable at the hole on the side of the engine. It should be slightly
battery. before (counterclockwise of) the 11 o’clock position
(2) Disconnect coil secondary cable at coil. (Fig. 13).
(9) Remove and discard the old distributor-to-en-
(3) Remove distributor cap from distributor (2
gine block gasket (Fig. 11).
screws). Do not remove cables from cap. Do not re-
move rotor. INSTALLATION—4.0L 6-CYLINDER ENGINE
(4) Disconnect the distributor wiring harness from (1) If the engine crankshaft has been rotated after
the main engine harness. distributor removal, cylinder number 1 must be re-


Fig. 13 Slot At 11 O’clock Position—4.0L Engine
turned to its proper firing stroke. Refer to the previ-
ous REMOVAL steps number 5 and 6. These steps
must be done before installing distributor.
(2) Check the position of the slot on the oil pump
gear. It should be just slightly before (counterclock- Fig. 14 Pin Alignment Holes
wise of) the 11 o’clock position (Fig. 13). If not, place
a flat blade screwdriver into the oil pump gear and shaft. When the distributor is fully seated to the en-
rotate it into the proper position. gine block, the centerline of the base slot should be
(3) Factory replacement distributors are equipped aligned to the clamp bolt mounting hole on the en-
with a plastic alignment pin already installed (Fig. gine (Fig. 16). The rotor should also be pointed at the
9). This pin is used to temporarily hold the rotor to 5 o’clock position.
the cylinder number 1 firing position during distrib- It may be necessary to rotate the rotor and distrib-
utor installation. If this pin is in place, proceed to utor shaft (very slightly) to engage the distributor
step number 8. If not, proceed to step number 4. shaft with the slot in the oil pump gear. The same
(4) If the original distributor is to be reinstalled, may have to be done to engage the distributor gear
such as during engine overhaul, the plastic pin will with the camshaft gear.
not be available. A 3/16 inch drift pin punch tool may
be substituted for the plastic pin.
(5) Remove the camshaft position sensor from the
distributor housing. Lift straight up.
(6) Four different alignment holes are provided on
the plastic ring (Fig. 14). For this application, use
‘‘4.0L 6-CYLINDER ENGINE ALIGN. HOLE’’ as
shown in figure 14.
Rotate the distributor shaft and install the pin
punch tool through the proper alignment hole in the
plastic ring (Fig. 14) and into the mating access hole
in the distributor housing. This will prevent the dis-
tributor shaft and rotor from rotating.
(7) Clean the distributor mounting hole area of the
engine block.
(8) Install a new distributor-to-engine block gasket
(Fig. 11).
(9) Install the rotor to the distributor shaft.
(10) Pre-position the distributor into the engine
while holding the centerline of the base slot in the 1
o’clock position (Fig. 15). Continue to engage the dis-
tributor into the engine. The rotor and distributor
will rotate clockwise during installation. This is due Fig. 15 Distributor Pre-position—4.0L Engine
to the helical cut gears on the distributor and cam-


(17) Connect the distributor wiring harness to the
main engine harness.
(18) Connect battery cable to battery.


CAUTION: Base ignition timing is not adjustable on
the 5.2L V-8 engine. Distributors do not have built in
centrifugal or vacuum assisted advance. Base igni-
tion timing and timing advance are controlled by
the powertrain control module (PCM). Because a
conventional timing light can not be used to adjust
distributor position after installation, note position
of distributor before removal.

(2) Remove coil high-tension cable and all spark
plug cables at distributor cap. Note and mark posi-
tion of cables (Fig. 17) before removal.

Fig. 16 Distributor Engaged Position—4.0L Engine
The distributor is correctly installed when:
• the rotor is pointed at the 5 o’clock position.
• the plastic alignment pin (or pin punch tool) is still
installed to distributor.
• the number 1 cylinder piston is set at top dead
center (TDC) (compression stroke).
• the centerline of the slot at the base of the distrib-
utor is aligned to the centerline of the distributor
holddown bolt hole on the engine. In this position,
the holddown bolt should easily pass through the slot
and into the engine.
No adjustments are necessary. Proceed to next
step. Fig. 17 Engine Firing Order—5.2L Engine
(11) Install the distributor holddown clamp and (3) Remove distributor cap from distributor (two
bolt. Tighten the bolt to 23 N⅐m (17 ft. lbs.) torque. screws).
(12) Remove the pin punch tool from the distribu- (4) Mark the position of distributor housing in re-
tor. Or, if the plastic alignment pin was used, remove lationship to engine or dash panel. This is done to
it straight down from the bottom of the distributor. aid in installation.
Discard plastic pin. Before distributor is removed, the number one cyl-
(13) If removed, install the camshaft position sen- inder must be brought to the top dead center (TDC)
sor to the distributor. Align the wiring harness grom- firing position.
met to the notch in the distributor housing. (5) Attach a socket to the crankshaft vibration
(14) Install the rotor. damper mounting bolt.
(6) Slowly rotate engine clockwise, as viewed from
CAUTION: If the distributor cap is incorrectly posi- front, until indicating mark on crankshaft vibration
tioned on distributor housing, the cap or rotor may damper is aligned to 0 degree (TDC) mark on timing
be damaged when engine is started. chain cover (Fig. 18).
(7) The distributor rotor should now be aligned to
(15) Install the distributor cap. Tighten distributor the CYL. NO. 1 alignment mark (stamped) into the
cap holddown screws to 3 N⅐m (26 in. lbs.) torque. camshaft position sensor (Fig. 19). If not, rotate the
(16) If removed, install the spark plug cables to crankshaft through another complete 360 degree
the distributor cap. For proper firing order, refer to turn. Note the position of the number one cylinder
the Specifications section at the end of this group. spark plug cable (on the cap) in relation to rotor. Ro-
See Engine Firing Order. tor should now be aligned to this position.


Fig. 18 Damper-To-Timing Chain Cover Alignment Fig. 20 Distributor Holddown Clamp—5.2L Engine
Marks—5.2L Engine (1) Clean top of cylinder block for a good seal be-
tween distributor base and block.
(2) Lightly oil the rubber o-ring seal on the distrib-
utor housing.
(3) Install rotor to distributor shaft.
(4) Position distributor into engine to its original
position. Engage tongue of distributor shaft with slot
in distributor oil pump drive gear. Position rotor to
the number one spark plug cable position.
(5) Install distributor holddown clamp and clamp
bolt. Do not tighten bolt at this time.
(6) Rotate the distributor housing until rotor is
aligned to CYL. NO. 1 alignment mark on the cam-
shaft position sensor (Fig. 19).
(7) Tighten clamp holddown bolt (Fig. 20) to 22.5
Fig. 19 Rotor Alignment Mark—5.2L Engine (8) Connect camshaft position sensor wiring har-
ness to main engine harness.
(8) Disconnect camshaft position sensor wiring (9) Install distributor cap. Tighten mounting
harness from main engine wiring harness. screws.
(9) Remove distributor rotor from distributor shaft. (10) Install spark plug cables in correct firing or-
(10) Remove distributor holddown clamp bolt and der (Fig. 17) to distributor cap. Be sure all spark
clamp (Fig. 20). Remove distributor from vehicle. plug cables are firmly connected into distributor cap
towers.
CAUTION: Do not crank engine with distributor re-
(11) Refer to the following, Checking Distributor
moved. Distributor/crankshaft relationship will be
Position.
lost.
CHECKING DISTRIBUTOR POSITION—5.2L ENGINE ONLY
INSTALLATION—5.2L ENGINE To verify correct distributor rotational position,
If engine has been cranked while distributor is re- connect the DRB scan tool to the data link connector.
moved, establish the relationship between distributor The data link connector is located in the engine com-
shaft and number one piston position as follows: partment. Gain access to the SET SYNC screen on
Rotate crankshaft in a clockwise direction, as the DRB.
viewed from front, until number one cylinder piston
is at top of compression stroke (compression should WARNING: WHEN PERFORMING THE FOLLOWING
be felt on finger with number one spark removed). TEST, THE ENGINE WILL BE RUNNING. BE CARE-
Then continue to slowly rotate engine clockwise until FUL NOT TO STAND IN LINE WITH THE FAN
indicating mark (Fig. 18) is aligned to 0 degree BLADES OR FAN BELT. DO NOT WEAR LOOSE
(TDC) mark on timing chain cover. CLOTHING.


Follow the directions on the DRB screen and start REMOVAL—5.2L V-8 ENGINE
the engine. With the engine running, the words IN The ignition coil is mounted to a bracket near the
RANGE should appear on the screen along with 0°. front of the right engine cylinder head on 5.2L en-
This indicates correct distributor position. gines (Fig. 22).
If a plus (+) or a minus (-) is displayed next to the
degree number, and/or the degree displayed is not
zero, loosen but do not remove the distributor hold-
down clamp bolt. Rotate the distributor until IN
RANGE appears on the screen. Continue to rotate
the distributor until achieving as close to 0° as pos-
sible. After adjustment, tighten clamp bolt to 22.5
The degree scale on the SET SYNC screen of the
DRB is referring to fuel synchronization only. It is
not referring to ignition timing. Because of this,
do not attempt to adjust ignition timing using this
method. Rotating the distributor will have no effect
on ignition timing. All ignition timing values are con-
trolled by the powertrain control module (PCM).

IGNITION COIL Fig. 22 Ignition Coil—5.2L Engine—Typical
The ignition coil is an epoxy filled type. If the coil (1) Disconnect the wiring and secondary cable from
is replaced, it must be replaced with the same type. the ignition coil (Fig. 22).
REMOVAL—4.0L 6-CYLINDER ENGINE WARNING: DO NOT REMOVE THE COIL MOUNTING
The ignition coil is mounted to the right side of the BRACKET-TO-CYLINDER HEAD MOUNTING BOLTS.
4.0L engine block next to the distributor (Fig. 21). THE COIL MOUNTING BRACKET IS UNDER ACCES-
SORY DRIVE BELT TENSION. IF THIS BRACKET IS
TO BE REMOVED FOR ANY REASON, ALL BELT
TENSION MUST FIRST BE RELIEVED. REFER TO
THE BELT SECTION OF GROUP 7, COOLING SYS-
TEM.

(2) Remove ignition coil from coil mounting bracket
(two bolts).

INSTALLATION—5.2L ENGINE
(1) Install the ignition coil to coil bracket. If nuts
and bolts are used to secure coil to coil bracket,
tighten to 11 N⅐m (100 in. lbs.) torque. If the coil
mounting bracket has been tapped for coil mounting
bolts, tighten bolts to 5 N⅐m (50 in. lbs.) torque.
(2) Connect all wiring to ignition coil.
Fig. 21 Ignition Coil—4.0L Engine
INTAKE MANIFOLD AIR TEMPERATURE SENSOR
(1) Disconnect the ignition coil secondary cable
from ignition coil (Fig. 21).
(2) Disconnect engine harness connector from igni-
tion coil.
(3) Remove ignition coil mounting bolts. Remove
coil.
INSTALLATION—4.0L ENGINE moval/installation procedures, refer to Group 14,
(1) Install ignition coil to bracket on cylinder block Fuel System.
with mounting bolts.
(2) Connect engine harness connector to coil.
(3) Connect ignition coil cable to ignition coil.


OXYGEN (O2S) SENSOR
For an operational description, diagnostics and re-
Fuel Systems, in this manual.

POWERTRAIN CONTROL MODULE (PCM)
The PCM is located on the cowl panel in the right/
rear side of the engine compartment (Fig. 23).

Fig. 24 Coolant Reserve/Overflow Tank Mounting

Fig. 23 PCM Location
REMOVAL
(1) Disconnect the negative battery cable at bat-
tery.
(2) Remove the coolant reserve/overflow tank (one
bolt and two nuts) (Fig. 24)
(3) Loosen the 60-Way connector mounting bolt
(Fig. 25).
(4) Remove the electrical connector by pulling
straight back.
(5) Remove the three PCM mounting bolts (Fig.
25).
(6) Remove PCM.
Fig. 25 PCM Mounting
INSTALLATION round each cable boot and spark plug (Fig. 26). These
(1) Check the pins in the PCM 60-way electrical shields protect the spark plug boots from damage
connector for damage. Repair as necessary. (due to intense engine heat generated by the exhaust
(2) Install PCM. Tighten three mounting bolts to 1 manifolds) and should not be removed. After the
spark plug cable has been installed, the lip of the ca-
(3) Engage 60-way connector into PCM. Tighten
ble boot should have a small air gap to the top of the
connector mounting bolt to 4 N⅐m (35 in. lbs.) torque.
heat shield (Fig. 26).
(4) Install coolant reserve/overflow tank (Fig. 24).
If removal of the heat shield(s) is necessary, remove
(5) Connect negative cable to battery.
the spark plug cable and compress the sides of shield
SPARK PLUGS for removal. Each shield is slotted to allow for com-
5.2L V-8 ENGINE ONLY: Spark plug cable heat pression and removal. To install the shields, align
shields are pressed into the cylinder head to sur-

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