Misfire detecting apparatus for internal combustion engine

摘要

A misfire detecting apparatus for detecting a misfire of an internal combustion engine based on a detected rotational speed parameter. A moving averaging calculation is performed with respect to data of the detected rotational speed parameter to calculate an averaged speed parameter, a number of the data being equal to a sampling number NTDC. A reference value of the averaged speed parameter and a relative speed parameter are calculated. The relative speed parameter is a deviation of the averaged speed parameter detected at every predetermined crank angle from the reference value. An integrated value of the relative speed parameter is calculated and a misfire determination is performed based on the integrated value. The sampling number (NTDC) is determined by an equation: NTDC = 720 / N × D¸
where (N) is a number of cylinders and (D ¸) is a sampling angular period (degree) of the rotational speed parameter.