| 摘要 |
PURPOSE:To prevent hunting of engine speed by interrupting complete closure of an ISC valve during low-temperature and low-speed engine conditions even if the ratio of intake air flow rate to engine speed is more than a predetermined value, and supplying proper amount of intake air. CONSTITUTION:An idling speed control (ISC) valve 32 for controlling idling speed serves to control the opening sectional area of an intake by-pass passage 30, and the valve 32 is completely closed when the ratio Q/N of intake air flow rate Q to engine speed N is more than, for example, 0.55l/rev. But, when the temperature of engine cooling water detected by a water-temperature sensor 56 is lower than 0 deg.C and the engine speed detected by a rotation-angle sensor 56 is less than 2,000rpm, complete closure of the valve 32 is interrupted. Thus, the intake air flow rate Q during low-temperature and low-speed engine conditions is ensured while the kinematic chain of complete closure of the valve 32- reduction of Q/N ratio-opening of the valve 32-increase in Q/N ratio-complete closure of the valve 32 is interrupted, thereby preventing the hunting of engine speed N. |
