MISFIRE DETERMINATION APPARATUS AND METHOD FOR INTERNAL COMBUSTION ENGINE

A CPU determines that misfires are occurring in a cylinder subject to determination of whether misfires are occurring when a value obtained by subtracting a rotation fluctuation amount ΔT30[n−2] from a rotation fluctuation amount ΔT30[n] is greater than or equal to a determination threshold. The rotation fluctuation amount ΔT30[n] is subject to the misfire determination. The rotation fluctuation amount ΔT30[n−2] is 360° CA earlier than the rotation fluctuation amount ΔT30[n]. When stopping fuel supply to a cylinder #1 and determining whether misfires are occurring in cylinder #4, the CPU determines whether misfires are occurring after executing a correcting process that corrects the determination threshold to a second determination threshold Δth2, which is less than a first determination threshold Δth1.