The failure of the fuel charge in one or more engine cylinders to ignite at the proper time. Engine misfire causes the engine to have a rough idle of hesitation upon acceleration.

A check engine light with a code P0300 is a common misfire code. Can also be spelled Missfire.

At idle, a misfire can be caused by a vacuum leak or restricted fuel injectors. A misfire under load- or acceleration is usually caused by an ignition component problem like a bad spark plug, ignition coil or spark plug wire.