Method and apparatus for detecting misfires in an internal combustion

Abstract

The invention provides an internal combustion engine misfire detection device for a motor vehicle in which an output of an internal combustion engine is transmitted via a torque converter to a drive shaft. A primary misfire detecting unit detects an internal combustion engine misfire condition including a possible false condition thereof; and an external cause detecting unit detects an influence associated with an external cause variation in terms of an operating condition variation transmitted from the drive shaft via the torque converter. A misfire judging unit judges whether the internal combustion engine misfire condition detected by the primary misfire detecting unit is a true misfire condition or a false misfire condition based on the detection output from the external cause detecting unit. A processing unit performs a predetermined processing to detect a misfire operating condition in response to a judgment by the misfire judging unit that the detected operating condition is a true misfire operating condition; and a misfire judgment disabling unit renders the misfire judging unit inoperative in response to a judgment by the misfire judging unit that the detected operating condition is a false misfire operating condition.