Abstract: An engine intake system having primary and secondary intake passages leading to the same combustion chamber. The secondary intake passage is provided with an auxiliary throttle valve which is opened under a relatively high load engine operation. The primary and secondary intake passages are respectively provided with first and second fuel injection valves which are controlled by an electronic control unit in accordance with engine operating conditions. The electronic control unit functions to determine a basic fuel supply quantity based on the intake airflow and the engine speed and modify the basic quantity by a compensation factor which is obtained from a compensation map. The compensation map is divided into two zones, the first zone substantially corresponding to the engine operating condition wherein the auxiliary throttle is closed, the second zone substantially corresponding to the engine operating condition wherein the auxiliary throttle valve is opened.