Patent ID: 7124019

Claim:
A method for diagnosing ignition system performance of an internal combustion engine having a plurality of spark plugs; a plurality of ignition coils, each one having a secondary winding coupled to a corresponding one of the plurality of spark plugs, each one of the plurality of ignition coils having a primary winding; and an engine control unit, such method comprising: operating the engine control unit to produce a sequence of spark ignition current pulses through the primary winding of the plurality of ignition coils, such current pulses producing voltage pulses across electrodes of the spark plugs, such voltage pulses producing sparks across the electrodes of the spark plugs and flyback voltages across the primary windings; producing, in response to the flyback voltages, digital signals representative of the time durations of the sparks; and comparing the digital signals to determine whether the spark time duration of one of the spark plugs is substantially different from the spark time durations of the other ones of the plurality of spark plugs.