APPARATUS FOR DETECTING ABNORMAL AIR-FUEL RATIO VARIATION AMONG CYLINDERS OF MULTI-CYLINDER INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To further accurately detect abnormal air-fuel ratio variation among cylinders with the usage of a catalyst temperature.

SOLUTION: A temperature Tc of a catalyst arranged in an exhaust passage of the multi-cylinder internal combustion engine is detected. A temperature parameter is calculated based on a detection value of the catalyst temperature. The presence or absence of abnormal air-fuel ratio variation among the cylinders is determined based on the value of the temperature parameter at the point of time t2 after the lapse of prescribed time from cold start time t1 of the internal combustion engine. An initial stage condition can be arranged for each detection time, and the detection accuracy can be improved.

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