| 摘要 |
A cylinder deviation of an actual air-fuel ratio before an air-fuel-ratio dither control is obtained based on a variation of an actual air-fuel ratio by the dither control, a variation amount of detected air-fuel ratio, and a cylinder deviation of detected air-fuel ratio before the dither control A cylinder deviation of actual air-fuel ratio of each cylinder is accurately estimated. When the number of times in which the cylinder deviation of air-fuel ratio exceeds a decision value is greater than a predetermined number, it is determined that an abnormality occurs in the cylinder.
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