Patent ID: 8281650

Claim:
A misfire determination device for an internal combustion engine that is coupled to a transmission via a hydraulic power transmission equipped with a lock-up clutch, wherein the misfire determination device determines that there is a possibility that a misfire has occurred when a rotation fluctuation amount of the internal combustion engine exceeds a predetermined threshold, and makes a misfire determination by determining whether a rotation fluctuation pattern of the internal combustion engine is a pattern specific to occurrence of a misfire, the misfire determination device comprising: a first misfire determination unit that makes a first misfire determination in which a misfire determination is made on the basis of whether, when the lock-up clutch is in a non-lock-up state, the rotation fluctuation pattern of the internal combustion engine substantially coincides with a first rotation fluctuation pattern specific to occurrence of a misfire in the non-lock-up state; and a second misfire determination unit that makes a second misfire determination in which occurrence of a misfire is determined on the basis of whether, when the lock-up clutch is in a lock-up state, the rotation fluctuation pattern of the internal combustion engine substantially coincides with a second rotation fluctuation pattern specific to occurrence of a misfire in the lock-up state.