Misfire-detecting system for internal combustion engines

A misfire-detecting system for detecting a misfire occurring in an internal combustion engine having an ignition system including at least one spark plug, engine operating condition-detecting means for detecting values of operating parameters of said engine, signal-generating means for determining ignition timing of said engine, based upon the detected values of said operating parameters of said engine and for generating an ignition command signal indicative of the determined ignition timing, and igniting means responsive to said ignition command signal for generating sparking voltage for discharging said at least one spark plug,

• said misfire-detecting system comprising:
• voltage value-detecting means for detecting a value of said sparking voltage generated by said igniting means after generation of said ignition command signal;
• and
• misfire-determining means for comparing the detected value of said sparking voltage with a predetermined voltage value, and for determining whether or not a misfire has occurred in said engine, based upon results of said comparison;
• said misfire-determining means effects said determination as to occurrence of said misfire, based upon at least one of a) a time period dependent upon an amount by which the detected value of said sparking voltage exceeds said predetermined voltage value, and b) a value proportional to an area of a portion of detected values of said sparking voltage exceeding said predetermined voltage value.