| 摘要 |
PURPOSE:To prevent offensive smell of exhaust gas, by employing a control constant corresponding to a second O2 sensor arranged in the downstream of a catalyst, and controlling the air-fuel ratio to the lean side for a predetermined time if the second O2 sensor is rich during fuel increment, when feedback control is made through a first O2 sensor arranged in the upstream of the catalyst. CONSTITUTION:A control circuit 10 operates such as rich skip quantity, lean skip quantity corresponding to a value detected through a second O2 sensor 15 arranged in the downstream of a catalyst converter 12, so as to make feedback control of air-fuel ratio corresponding to the operating condition based on said control constant and a value detected through a first O2 sensor 13 arranged in the upstream of the catalyst converter 12. When synchronous increment is carried out during acceleration and the output from the second O2 sensor 15 exhibits rich, control to lean side is carried out for a predetermined time based on a value detected through the first O2 sensor 13 thereafter reset control to a theoretical air-fuel ratio is carried out.
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