| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem in which it is difficult to diagnose the existence of an abnormality in an individual air-fuel ratio of a plurality of cylinders with high accuracy based on a detection value of an air-fuel ratio sensor 36 disposed at the downstream side of a merging part J where exhaust gases discharged from each of the plurality of cylinders merge. SOLUTION: The exhaust gas discharged from a combustion chamber 26 of each cylinder flows near the air-fuel ratio sensor 36 via the merging part J. An ECU 40 estimates the air-fuel ratio of each cylinder based on the detection value of the air-fuel ratio sensor 60. When a deviation amount between the air-fuel ratios of each of the cylinders is a predetermined amount or more, it is determined that there is an abnormality in the air-fuel ratios. When the discharged exhaust gas amount from each cylinder is not a predetermined amount or more, before determination of the existence of an abnormality, the intake air amount is increased and the ignition timing is delayed. COPYRIGHT: (C)2009,JPO&INPIT
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