Control system for internal combustion engine

A control system for a mixture-compressing internal combustion engine comprising a carburetor means, an intake manifold means, a throttle valve means disposed in the intake manifold means, and an idle channel means for bypassing the throttle valve means, an additional channel means only forming an air channel bypasses the carburetor means and throttle valve means for introducing air into the intake manifold means, the additional channel means terminates in the intake manifold means at a position downstream of the idle channel means, first valve means are provided for controlling a communication between the additional channel means and the intake manifold means, the first valve means is located between the throttle valve means and inlet openings of the internal combustion engine, a diaphragm means is connected to the valve means for controlling an opening and closing of the valve means, line means are interposed between the diaphragm means and the intake manifold means for enabling an exposing of a side of the diaphragm means facing away from the first valve means to intake manifold vacuum, a further valve means, controlled by intake manifold vacuum, is disposed in the line means for enabling a venting of the diaphragm means and opening of the first valve means when the intake manifold vacuum is above an idle value, during a coasting operation of the engine whereby the side of the diaphragm means facing away from the first valve means can be evacuated to activate the first valve means so that air exclusively flows into the intake manifold through the air channel means, thereby permitting an introduction of air into the intake manifold means through the additional channel means, and means are provided for controlling a positioning of the further valve means.