The engine misfiring means that a car's engine skips over one of the processes of its combustion cycle. This generally causes the engine to run rough, jerk, or buck. It also causes the engine to run inefficiently. There are several types of engine misfires. Some of the common occurrences include lean misfires, ignition misfires, and mechanical misfires. Lean misfire refers to an engine misfiring because the air-fuel ratio is not properly balanced. Ignition misfires occur when either the spark plug, wire, distributor, or ignition coil fail, causing an engine misfire on the specific cylinder.