What causes the exhaust pipe to smoke?

1. Engine is running rich: This means the engine is getting more fuel than it needs, which causes unburned fuel to exit the exhaust pipe as smoke. This can be caused by a variety of factors, such as a faulty fuel injector, a bad oxygen sensor, or a clogged air filter.

2. Engine is burning oil: This can happen when the piston rings are worn or damaged, or when the oil level is too high. Oil smoke is typically blue in colour and has a pungent odour.

3. Coolant is leaking into the engine: This can happen when the head gasket is blown, or when there is a crack in the engine block. Coolant smoke is typically white in colour and has a sweet smell.

4. Transmission fluid is leaking into the engine: This can happen when the transmission cooler lines are damaged, or when the transmission fluid level is too high. Transmission fluid smoke is typically red or brown in colour and has a burnt smell.

5. Catalytic converter is damaged: The catalytic converter is responsible for converting harmful pollutants into less harmful compounds. When the catalytic converter is damaged, it can cause the exhaust to smoke. Catalytic converter smoke is typically black in colour and has a strong, pungent odour.