| 摘要 |
PURPOSE:To make proper control of air-fuel ratio at all times by making feedback control of air-fuel ratio through an air-fuel ratio sensor arranged in the downstream of a catalyst converter when deterioration of catalyst in the catalyst converter is detected. CONSTITUTION:First and second air-fuel ratio sensors A1, A2 are arranged at the upper and lower sides of a catalyst converter. Means B for operating an air-fuel ratio feedback control constant corresponding to the output from a second air-fuel ratio sensor A2 is provided. Furthermore, means C1, C2 for operating air-fuel ratio correction quantity corresponding to outputs from respective air-fuel ratio sensors A1, A2 and predetermined air-fuel ratio feedback control constant or an air-fuel ratio feedback control constant operated through means B are provided. Means D for judging deterioration of catalyst converter is further provided. Means E for regulating air-fuel ratio of engine based on air-fuel ratio correction quantity operated respectively through second and first means C2, C1 according as deterioration of catalyst is judged or not is provided.
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