| 摘要 |
PROBLEM TO BE SOLVED: To suppress occurrence of engine stalling due to insufficient air amount when an idle rotational speed is adjusted. SOLUTION: A main bypass passage 22 and an auxiliary bypass passage 24 through which the upstream and downstream sides of a throttle valve 19 are communicated with each other, are arranged in the inlet passage 11 of an engine 1 by being bypassed the throttle valve 19, and an idle speed control valve (ISCV) 23 and an idle adjusting screw 25 adjusted from the outside are arranged on the way of the main bypass passage 22 and the auxiliary bypass passage 24. In the case that the screw 25 is adjusted from the outside when an idle rotational speed is adjusted, an electronic controller (ECU) 51 fixedly controls the opening of the ISCV 23 at a predetermined opening. Fixing control is executed on the basis of a final duty ratio set on the basis of a leaning value when the ISCV 23 is controlled just before the fixing control. Therefore, an enough air flow corresponding to sludge accumulation can be secured even though sludge is secularly accumulated. |
