Method and apparatus for controlling the idling speed of an engine

Abstract

An engine has a main intake passage in which a throttle valve is disposed. A bypass passage is branched off from the main intake passage 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. In an electronic control unit, the mean value of the step position is stored, and a lower limit of the step position is calculated from the mean value of the step position. When the engine is idling after it has been and the stepper motor is rotated in a direction wherein the flow control valve closes the rotating operation of the stepper motor is stopped when the step position of the stepper motor reaches thelower limit of the step position. This allows for precise control of the flow control valve, while preventing the sudden rapid closing of the valve, thus improving engine performance.

Dependencies are inferred from the claim text.