INTERNAL COMBUSTION ENGINE DIAGNOSTIC DEVICE AND INTERNAL COMBUSTION ENGINE DIAGNOSTIC METHOD

摘要

An internal combustion engine diagnostic device (14) and an internal combustion engine diagnostic method identify an abnormal cylinder having an abnormal air-fuel ratio among a plurality of cylinders (32) during the operation of an internal combustion engine (16). The internal combustion engine diagnostic device (14) comprises: an air-fuel ratio control unit (84) for changing the air-fuel ratio in a stepwise manner by controlling a fuel injection amount adjusting means (20) that adjusts the fuel injection amount of each of the plurality of cylinders (32); and an abnormal cylinder identification unit (84) for identifying an abnormal cylinder on the basis of the relationship between each air-fuel ratio changed in a stepwise manner and the number of misfires occurring in the plurality of cylinders (32), the number being counted by a misfire counter (20) for each air-fuel ratio changed in a stepwise manner.