Method and apparatus for controlling the idling speed of an engine

摘要

An engine has a main intake passage having a throttle valve therein. A bypass passage is branched off from the main intake passage located upstream of the throttle valve and is connected to the main intake passage located downstream of the throttle valve. A flow control valve, actuated by a stepper motor, is arranged in the bypass passage. When the idling speed of the engine is increased beyond a predetermined upper limit of the engine speed, the stepper motor is rotated in a rotating direction wherein the flow area of the flow control valve is reduced. Contrary to this, when the idling speed of the engine is reduced below a predetermined lower limit of the engine speed, the stepper motor is rotated in a direction wherein the flow area of the flow control valve is increased.