| 摘要 |
PURPOSE:To maintain a satisfactory operating performance of an engine, by determining a reference rotational speed which decreases as the selected gear ratio of a speed change unit decreases, in accordance with the selected shift position, and by controlling the air-fuel ratio to be lean when an actual rotational speed exceeds the reference rotational speed and upon low load operation of the engine. CONSTITUTION:Upon operation of an engine, in a control circuit 22 which receives signals from sensors 20, 34, 36, 40, 42, 48 for detecting various operating conditions, a reference rotational speed NR is searched in accordance with the present gear shift position. This reference rotational speed NR is determined such that the smaller the gear ratio, the smaller the speed NR becomes. The determined reference rotational speed NR is compared with the present actual engine rotational speed Ne. Further, if Ne>NR, when a lean mixture condition is establied, that is, the engine is in a low load but high rotational speed range in which the temperature of cooling water is below a predetermined value (about 75 deg.C), and the opening degree of a throttle valve is less than, for example, 30 deg.. A lean mixture compensating coefficient is set in accordance with the pressure of an intake pipe. Further, a reference injection time which is obtained by calculating the rotational speed of the engine and the pressure of the intake-air pipe, is compensated.
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