Abstract: The invention discloses an apparatus for adjusting or actuating an air throttle valve positioned in the intake manifold of an internal combustion engine which is supplied by air under pressure. The air throttle valve is held in a closed position by a spring when the engine is in the cold starting phase. Air is supplied to the engine through a by-pass valve when the air throttle valve is closed. The air throttle valve is opened against the force of the spring in response to a predetermined pressure or vacuum in the intake manifold at the end of the cold starting phase. The air throttle valve is held in an open position by an electro-magnetic structure which is effective when an ignition circuit of the vehicle is energized or by a detent structure which is effective when the engine or exhaust temperatures are at predetermined levels.