is the continued running of a spark-ignited engine after the ignition is turned off; also known as dieseling. There are two basic causes of afterrunning; surface ignition and compression ignition. In surface ignition, the surfaces of the combustion chamber remain hot enough to provide a source of ignition after the spark ignition is terminated. In compression ignition, the conditions of temperature, pressure, fuel composition, and engine idle speed allow ignition to continue.

Also see compression ignition.