Patent ID: 7062373

Claim:
A misfire detection apparatus of an internal combustion engine, comprising: at least one angle sensor for detecting rotation angle of the internal combustion engine; at least one an Electronic Control Unit for performing fuel injection and ignition control based on rotation information of the angle sensor; plural ignition coils for generating a high voltage for ignition based on a drive signal from the Electronic Control Unit; plural spark plugs, as the high voltage for ignition of the ignition coil is applied, for generating ignition spark and igniting air fuel mixture; bias means for applying a bias voltage for ion current detection to the spark plug; ion current detection means for detecting ion current; misfire determination means for making a misfire determination based on output signal of the ion current detection means; failure determination means for making a failure determination of the misfire determination means based on time change of rotation information of the internal combustion engine when the misfire determination means determines that misfires occur successively in a specific cylinder of the internal combustion engine.