MISFIRE DETECTION DEVICE FOR INTERNAL COMBUSTION ENGINE, MISFIRE DETECTION METHOD FOR INTERNAL COMBUSTION ENGINE, AND MEMORY MEDIUM

A misfire detection device and method for an internal combustion engine are provided. A deactivating process deactivates combustion control for air-fuel mixture in a deactivated cylinder. An instantaneous speed variable indicates a speed in a case where a crankshaft rotates by a specific angle. The specific angle of the first instantaneous speed variable is a first angle. The specific angle of the second instantaneous speed variable is a second angle greater than the first angle. A second determining process determines whether a misfire has occurred from a magnitude of a rotation fluctuation amount of a subject of determination, instead of a relative magnitude of the rotation fluctuation amount of the subject of the determination relative to a reference rotation fluctuation amount, when the reference rotation fluctuation amount is a rotation fluctuation amount of the deactivated cylinder during the execution of the deactivating process.