MISFIRE DETECTION DEVICE FOR INTERNAL COMBUSTION ENGINE

A CPU performs a regeneration process for a GPF by stopping combustion control of cylinder #1 and causing an air-fuel ratio of an air-fuel mixture in the other cylinders to be richer. The CPU calculates a rotational fluctuation amount which is used to detect random misfires in which a misfire rate in a predetermined period is equal to or greater than a predetermined proportion by calculating a difference in time et3txdh in which a crank shaft rotates by 30°CA. At the time of performing the regeneration process, the CPU calculates the rotational fluctuation amount based on a value obtained by removing an influence of torsion of a damper from the time et3txdh. When the influence of torsion is removed, 0.5th-order rotation and harmonics thereof are selectively used using a filter process.