| 摘要 |
PROBLEM TO BE SOLVED: To precisely detect a misfire by combustion-operating all cylinders of an internal combustion engine when establishment of a forced misfire detecting condition is judged, and detecting the misfire every cylinder with respect to all the combustion-operated cylinders. SOLUTION: The average value of respective engine speeds in ignition period for first, second, third and fourth cylinders is calculated, and the difference from the previous calculated value is calculated. The calculated change quantity is compared with a misfire judgment threshold, and when the absolute value of the difference is the absolute value of the calculated change quantity or more it is judged that the ignited cylinder misfired last time. Accordingly, misfire detection start condition is judged by judging whether an engine 10 is in start cranking where the rotation is unstable or not, and when it is judged that the engine is not in cranking, establishment of the misfire detection start condition is judged. It is judged whether forced misfire detection condition is established or not, and when this condition is established, all cylinders are combustion-operated. The misfire detection is performed with respect to all the cylinders by use of a misfire judgment threshold.
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