Engine idling rotational speed control device

摘要

A stepping motor is driven to control an opening area of an intake air flow rate control valve such that an engine rotational speed in a substantially full-close position of a throttle valve is brought into a target rotational speed range related to at least an engine coolant temperature. An intake air quantity into an engine and engine rotational speed are detected to determine a ratio of the intake air quantity to the engine rotational speed. Downward control to the intake air flow rate control valve is inhibited when a ratio of intake air quantity into an engine to the engine rotational speed is smaller than a predetermined reference.