Idle speed control system for vehicle engines

摘要

An idling speed control system for automotive vehicle engines is disclosed. A throttle valve bypass passage for intake air is provided with an air control valve of the on-off type. The air control valve is electrically energized by a pulse train of substantially constant pulse repetition rate and pulse duration modulation so that the duty cycle of the valve is varied according to deviation of the engine idling speed from a set point value. The pulse repetition rate of the energizing pulses is higher than the frequency at which the engine can respond to air supply pulsations in the intake manifold.