Ignition of the air-fuel charge in the combustion chamber before the spark plug ignites the mixture. Also called "knocking" or "pinging".

Ignition of the fuel/air mixture in a gasoline engine before the spark plug fires. Often caused by incandescent fuel or lubricant deposits in the combustion chamber, it wastes power and may damage the engine.

Early ignition of fuel in the cylinder, sometimes due to glowing carbon deposits in the combustion chamber. Preignition can be damaging since combustion takes place prematurely.

Any ignition of the fuel in an engine before the spark plug fires, often caused by engine deposits, that wastes power and may damage the engine.

A damaging engine condition wherein the air/fuel mixture ignites spontaneously due to hot spots in the combustion chamber. Causes include engine-overheating, spark plugs that are the wrong heat range (too hot), sharp edges on the combustion chamber, low o