This document describes an experimental investigation into the effects of engine coolant temperature on exhaust emissions from a 3-cylinder, 4-stroke spark ignition engine. The experiments varied the engine coolant temperature from 45°C to 85°C at different engine speeds and loads. The results show that raising the coolant temperature decreases hydrocarbon emissions, while lowering the coolant temperature in the cylinder head decreases nitrogen oxide emissions. Both hydrocarbons and nitrogen oxides emissions generally decreased as the coolant temperature increased from 75°C to 85°C across different engine loads. The study confirms that exhaust emissions are dependent on engine coolant temperature.