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 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 determining whether or not a misfire has occurred in said engine, based upon results of said comparison;
• said misfire-determining means having period-limiting means for setting a limited comparison period;
• said misfire-determining means effecting said determination as to occurrence of said misfire, based upon results of said comparison between the detected value of said sparking voltage and said predetermined voltage value, obtained within said limited comparison period.