INTERNAL COMBUSTION ENGINE SPEED CONTROLLER FOR CONTROLLING A THROTTLE VALVE BYPASS WITH RESPECT TO THE ATMOSPHERIC PRESSURE

An engine speed control apparatus including an air control valve which controls the cross-sectional area of a bypass passage provided so as to bypass the throttle valve of the engine. The apparatus also includes a control unit which controls a degree of opening of the air control valve on the basis of a synthesized quantity which is obtained by synthesizing a basic air quantity for maintaining a target engine speed and an engine speed feed-back correction quantity which effects to eliminate an error between the target speed and an actual engine speed. An atmosphere pressure sensor is used to detect an atmospheric pressure, and a correction circuit is used to ensure that the synthesized quantity corresponds with the detected atmospheric pressure the engine is started.