What Can Cause a Car Engine to Smoke?

By Staff WriterLast Updated Apr 14, 2020 11:46:02 PM ET
Getty Images AsiaPac/Getty Images Sport/Getty Images

Reasons for a smoking engine include a clogged air filter, blocked manifold, oil leaking on to the exhaust system, leaking head gasket or a cracked cylinder head. Regardless of the reason, it is important to visit a mechanic if a car engine starts to smoke, or permanent damage can happen.

If the engine is giving off white smoke in a gasoline engine, it is likelycoolant or water being vaporized in the combustion chamber. This can be caused by the head gasket leaking, a cracked engine block or cracked cylinder head. In a diesel vehicle, white smoke can mean that the fuel is not burning due to a faulty injection system, incorrect timing or the engine overheating. However, in both engine types, it could also be due to the engine not being warm enough.

Black or gray smoke in any engine can be caused by fuel combustion remaining incomplete. Causes for all engines include oil leaking onto the exhaust system, a clogged air filter or incorrectly timed ignition. In a gasoline engine, it can be caused by a blocked manifold or carburetor, choke, fuel injection or emission system malfunction. In a diesel engine, it can be caused by a faulty injection system, the wrong grade of fuel, incorrect timing or the engine overheating.

Blue smoke is due to engine oil being burned or atomized and can be caused by worn piston rings, valves or cylinders. In a gasoline engine, it can also be caused by oil leaking into the combustion chamber, and in a diesel engine, it can be caused by high levels of engine oil.