Misfire Monitor Diagnostic Operation

Misfire is monitored as a function of the Combustion Quality (CQ) signals generated from the ignition current sense system. Combustion signals represent degree of combustion in each cylinder. Misfire is detected when combustion signal is below a predetermined value. Misfire ratio is calculated once every 100 engine cycles. For example, on a 6-cylinder engine, 600 ignition plug sparks occur every 100 cycles and if a misfire occurs 12 times during that time, the misfire ratio is 12/600 x 100 = 2%.