PURPOSE: To control the engine in an optimum manner in the engire region of load by a method wherein VC negative pressure taken out from a VC hole located in the downstream of a throttle valve is controlled by venturi negative pressure and EGR and the air-fuel ratio are controlled in synchronization in accordance with the controlled VC negative pressure.

CONSTITUTION: An EGR valve 22 is provided in an EGR passage 21 returning a part of exhaust gas to an intake passage 20 and the negative-pressure chamber of the valve is connected with the 1st VC hole 24 through the intermediary of the 1st negative-pressure passage 26 fitted intermediary with a thermal valve 25. The 1st negative-pressure passage 26 is opened to the air through the intermediary of the 1st air introducing passage 27 fitted intermediately with a venturi negative pressure transducer valve 28. In addition, the 1st and 2nd air introducing passage 35 and 36 connected with the 2nd and 3rd negative pressure passages 32 and 34 respectively are made capable of being opened to the air alternately by switching by means of a negative-pressure adjusting valve 37, while the negative pressure chamber 38 of the valve 37 is connected to the 2nd VC hole 40 through the intermediary of the 4th negative pressure passage 39 fitted intermediately with a delay valve 55. The 4th negative pressure passage 39 is opened to the air through the intermediary of a VC negative-pressure controlling valve 46.