| 摘要 |
PURPOSE:To prevent an engine from knocking, by retarding the ignition timing of the engine by a predetermined amount and by enriching the air-fuel ratio of the engine when wire breakage or the like occurs in a knock sensor so that a fail safe measure is effected. CONSTITUTION:During engine operation, a control unit 8 compensates a fuel injection amount which is computed in accordance with output signals from a crank angle sensor 1 and an airflow meter 3, in accordance with an output signal from an oxygen sensor 5 to carry out air-fuel ratio feed-back control in order to obtain a stoichiometric air-fuel ratio. Further, an ignition timing (spark advance) which is computed in accordance with an output signal from the crank angle sensor 1 is compensated when a knock sensor 6 detects knocking, in accordance with a spark retardation compensating amount which has been obtained in accordance with the intensity of knocking at that time. In this arrangement, when an abnormality in the knock sensor 6 is detected, the ignition timing is retarded by a predetermined amount, and further the fuel injection amount is compensated to the increased by a certain predetermined rate, thereby the air-fuel ratio is controlled to the enriched.
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