Abstract: A fuel supply control system for an internal combustion engine comprises deceleration detecting device for detecting a predetermined decelerating condition of the engine, and fuel supply decreasing device for decreasing the supply of fuel to the engine when the predetermined decelerating condition is detected by the deceleration detecting device. A first counting device starts to count a first predetermined time period when the high-load detecting device detects that the engine has left the predetermined high-load condition. An inhibiting device inhibits the fuel supply decreasing device from operating when the deceleration detecting device detects the predetermined decelerating condition of the engine before the first counting device completes counting the first predetermined time period. A second counting device counts a second predetermined time period while the high-load detecting device is detecting the predetermined high-load condition of the engine.

Abstract: A fuel supply control system for an internal combustion engine having a throttle body, and a fuel injection valve arranged in an intake manifold upstream of the throttle body for supplying fuel to all cylinders. An air throttle valve has a valve body having a notched opening formed therein and disposed to be opposite the nozzle of the fuel injection valve to increase the flow speed of intake air in the vicinity of the nozzle when the air throttle valve is fully closed. An electronic control unit controls the fuel injection valve in response to operating conditions of the engine. The electronic control unit causes the air throttle valve to be fully closed when a predetermined low rotation-speed operating condition of the engine, in which at least the rotational speed of the engine is lower than a predetermined value, is satisfied. The predetermined value of the rotational speed of the engine is set such that the lower the atmospheric pressure the smaller the predetermined value.

Abstract: A method of controlling the air-fuel ratio of a mixture of fuel supplied to an internal combustion engine. Feedback control is effected to response to an output from an exhaust-gas concentration sensor to bring the air-fuel ratio to a predetermined value when the engine is in a predetermined medium-load operating region. It is determined whether or not the engine is in a predetermined high-load operating region in which the feedback control is interrupted for bringing the air-fuel ratio to a value smaller than the predetermined value, and whether or not the engine is in a predetermined low-load operating region in which the feedback control is interrupted for bringing the air-fuel ratio to a value larger than the predetermined value.