| 摘要 |
PURPOSE:To prevent the discrepancy of air-fuel ratios owing to inactivation, by controlling air-fuel ratios for near a target air-fuel ratio based on learning values regardless of the output of an O2 sensor during the continuation of a low load operation after an engine low load operation condition continues for more than a prescribed time. CONSTITUTION:A control circuit 20 controls air-fuel ratios for a target air-fuel ratio via an electromagnetic valve 9, based on the outputs of an absolute pressure sensor 10 at the downstream position of a throttle valve, a cooling water temperature sensor 12, an O2 sensor 14, a car speed sensor 16, an atmospheric pressure sensor 17, and a crank angle sensor 11 and the like. An engine 5 is judged to be a low load operation condition under an condition that the revolution number of the engine is, for example, less than 1,050rpm and an absolute pressure in an intake manifold is less than 300mmHg, and while the low load operation condition continues after the condition continues for more than about 20sec, the air-fuel ratios are controlled to the target air-fuel ratio based on learning values corresponding to the irregularity of a base air-fuel ratio and the deterioration of the O2 sensor.
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