Patent ID: 8046155

Claim:
A method of monitoring for a misfire event in an internal combustion engine, the method comprising: monitoring signals representative of engine speed for successive engine revolutions at least subsequent to a firing event; storing the monitored speed signals for each revolution in a non-transitory machine readable storage medium; processing the stored monitored speed signals to detect changes in the monitored speed signals; detecting changes in the monitored speed signals indicative of an actual misfire event; and changing a misfire count in response to detected changes in the monitored speed signals indicative of the firing event being an actual misfire event; wherein processing the monitored speed signals comprises: generating speed difference signals in respect of the firing event over successive engine revolutions at least subsequent to the firing event; comparing the speed difference signals with respective calibration threshold values representative of different potential misfire events to determine a set of values, each value having either a first value where a speed difference signal crosses its respective calibration threshold or a second value where a speed difference signal does not cross its respective calibration threshold; logically comparing the determined set of values to a predetermined misfire pattern having a set of values to produce a comparison result pattern; and confirming the actual misfire event or not based on the comparison result pattern; wherein the misfire count is changed in response to determining a set of comparison result indicators, of the comparison result pattern, indicative of an actual misfire event.