| 摘要 |
PURPOSE:To enable to control the idling speed in a highly stable and reliable manner, by controlling the idling speed to increase the same by a prescribed value on the basis of the output of a fluctuation detecting means for detecting long-period fluctuations of the engine speed due to misfiring. CONSTITUTION:A by-pass passage 46 is disposed in the manner of by-passing a throttle valve 42 disposed in an intake passage 26, and a control valve (proportional solenoid valve) 48 is provided in the by-pass passage 46. In controlling the control value 48 by a control unit 52, the control valve 48 is feedback controlled to converge the engine speed detected by an engine-speed sensor 54 to an aimed idling speed. Further, the control unit 52 incorporates therein a fluctuation detecting means for detecting long-period fluctuations of the engine speed due to misfiring and controls the idling speed to increase the same by a prescribed value when fluctuation of the engine speed is detected. With such an arrangement, it is enabled to secure stable operation of an engine by decreasing the level and duration of the engine-speed drop at the time when fluctuation of the engine speed is caused.
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