| 摘要 |
PURPOSE:To make it possible to simply and rapidly determine occurrence of abnormality, by comparing the actual value of engine supply air volume with the expected value so that, when the actual value exceeds the expected value, occurrence of an abnormality in an idle rotational speed control device is determined. CONSTITUTION:The rotational speed of idling is controlled to a desired rotational speed by controlling, through a control circuit 40, the opening degree of a solenoid valve 22 disposed in a bypass passage 21 which bypasses a throttle valve 3 in an intake-air passage 12. In this arrangement, the control circuit 40 receives an output signal from an air-flow sensor 2 to obtain an actual engine intake-air volume Q. Further, the control circuit 40 receives output signals from a throttle valve sensor 29 and a crank angle sensor 32, and searches a predetermined map in accordance with the opening degree of the throttle valve and the rotational speed of the engine thus obtained, to obtain an expected basic intake- air volume A. Further, the thus obtained volume is suitable compensated to obtain an expected intake-air volume C. By comparing an actual intake-air volume Q with the expected intake-air volume C, if Q>C, occurrence of abnormality is determined so that fail-safe control is carried out. |
