Misfire determination apparatus for internal combustion engine

Abstract

A misfire determination apparatus for an internal combustion engine including a rotational speed detector detecting a rotational speed of an engine and a microprocessor. The microprocessor is configured to perform calculating a misfire parameter having a correlation with a change amount of the rotational speed in a combustion stroke of each of a plurality of cylinders and increasing as an increase amount of the rotational speed is large based on the rotational speed detected by the rotational speed detector, and determining that a single-cylinder misfire has occurred when the misfire parameter is less than a first predetermined value, while determining that the single-cylinder misfire or a multi-cylinder misfire has occurred when the misfire parameter is less than a second predetermined value greater than the first predetermined value.