Control method and apparatus for internal combustion engine

Abstract

An apparatus for controlling air supply to an internal combustion engine comprises a main intake pipe for supplying air to the engine, a throttle valve disposed in the main intake pipe for controlling flow rate of the air supplied to the engine in dependence on depression of an accelerator pedal, a plurality of bypass passages disposed in parallel with the main intake pipe for allowing the air to be supplied to the engine by bypassing the throttle valve, a plurality of bypass valves installed in the plurality of bypass passages, respectively, a diagnosis means for diagnosing the throttle valve and devices associated therewith as to occurrence of abnormality, and a controller responsive to detection of the abnormality to close the throttle valve while allowing the bypass valves to control the intake air flow in dependence on depression of the accelerator pedal. The controller responds to detection of the abnormality for shifting a range of engine operation from a normal operation range. Besides, upon occurrence of abnormality in the throttle valve and the associated devices, the controller converts the opening degree of the bypass valves determined arithmetically on the basis of a driving force required for driving the bypass valves into a corresponding opening degree of the throttle valve, and controls the speed of the motor vehicle and a fuel supply to the engine on the basis of the converted opening degree. A limp-homing operation of the motor vehicle can be ensured.