MISFIRE DETECTING DEVICE AND METHOD FOR INTERNAL COMBUSTION ENGINE

Time required by a crankshaft to rotate 30° CA from a compression top dead center is defined as time T30. A CPU calculates a rotation fluctuation amount ΔT30 related to a cylinder subject to determination of a misfire by subtracting a value related to a cylinder in which a compression top dead center occurred immediately before the cylinder subject to the determination from a value related to the subject to the determination. The rotation fluctuation amount ΔT30 that corresponds to a cylinder in which a combustion operation is stopped is used as a reference value ΔT30ref. When a combustion operation is performed, it is determined that there is a misfire if the absolute value of the difference between the rotation fluctuation amount ΔT30 and the reference value ΔT30ref is less than or equal to a determination value Δth.