MISFIRE DETECTION APPARATUS AND MISFIRE DETECTION METHOD FOR MULTI-CYLINDER ENGINE

A misfire detection apparatus for multi-cylinder engine is configured to detect a misfiring state in which any of a plurality of cylinders in an engine is misfiring, the engine including: the plurality of cylinders, and a catalyst device configured to purify exhaust gas from the plurality of cylinders. The apparatus includes: a rotation sensor configured to detect a rotational speed of the engine, and an electronic control unit including a processor and a memory coupled to the processor and configured to control operation of the engine. The processor detects the misfiring state of the engine based on the rotational speed of the engine detected by the rotation sensor.