| 摘要 |
A first O2 sensor is installed upstream, and a second O2 sensor downstream, of the catalyst converter in the exhaust passage of an engine. It is judged from the output of this first O2 sensor whether the air-fuel ratio (AFR) has changed beyond the theoretical AFR, and AFR feedback control is performed based on the judgment result. A correction value of an AFR feedback control coefficient is previously stored in each learning area in a memory corresponding to the engine running conditions, and the fuel injection amount supplied by the fuel injector is corrected based on this correction value. The correction value is updated by an updating amount corresponding to the magnitude of the difference between the output of the second O2 sensor and a value corresponding to the theoretical AFR. Undershoot or overshoot of the AFR is thereby prevented, and the AFR is rapidly brought within a desired range.
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