| 摘要 |
An engine air-fuel ratio control system (12) is configured to use a rich air-fuel ratio immediately after starting an engine (1) such that the air-fuel ratio converge rapidly toward a stoichiometric value and then afterwards start an air-fuel ratio feedback control. Upon determining an air-fuel ratio sensor (17) is active, a target air-fuel ratio revising coefficient TFBYA is decreased at a higher rate than the rate used before the air-fuel ratio sensor (17) was determined to be active. Air-fuel ratio feedback control starts when the air-fuel ratio corresponds to a stoichiometric air-fuel ratio. Afterwards, when either air-fuel ratio feedback control starts or when the engine enters a high rotational speed/high load region (TFBYA0 > 1) where it operates using a rich air-fuel ratio, whichever occurs first, an unburned fuel quantity compensating value is set based on the stabilization fuel quantity increasing factor in effect at that point in time and added to the target air-fuel ratio revising coefficient while, simultaneously, the stabilization fuel quantity increasing factor is set to zero.
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