Misfire detecting apparatus using difference in engine rotation speed variance

摘要

In a misfire detecting apparatus of an internal combustion engine, a difference in rotational-speed variance from a rotation signal NE of a crankshaft and the difference in rotational-speed variance is compared with a predetermined misfire criterion value in order to make a determination as to whether a misfire has occurred in the internal combustion engine. The misfire detecting apparatus is applied to a six-cylinder internal combustion engine. An ECU employed in the misfire detecting apparatus is used for calculating differences in rotational-speed variance by using a 720 DEG CA, a 360 DEG CA, and a 120 DEG CA differential techniques. The differences in rotational-speed variance computed by using the differential techniques are each compared with a respective predetermined misfire criterion value. An outcome of the comparison is used for updating a misfire count. The ECU makes a final determination as to whether a misfire has occurred in the internal combustion engine from data of a plurality of such misfire counts.