Control apparatus for an internal combustion engine having a carburetor

Abstract

An apparatus for controlling the operation of an internal combustion engine having a carburetor which, controls the air-fuel ratio of the air-fuel mixture supplied to the engine in the steady operating condition of the engine on the basis of predetermined data determined relative to the engine crankshaft rotation speed and intake vacuum and stored in a memory. A three-way catalyst purifies engine exhaust gases, and an output signal from an O.sub.2 sensor in the exhaust system is fed back for the control of the air-fuel ratio in the engine exhaust gases. A circuit checks whether this feedback control is normally carried or not. The air-fuel ratio supplied to the engine in an unsteady operating condition of the engine is controlled by regulating the fuel and air supplied to the engine while bypassing the carburetor, by the sensed values of the intake vacuum, engine crankshaft rotation speed and engine temperature and also depending on the throttle valve position. To control the rate of exhaust gas recirculation, an upper limit and a lower limit of the rate of opening of a recirculation rate regulating valve are determined on the basis of the sensed throttle valve opening, and other predetermined data determined relative to the engine crankshaft rotation speed and intake vaccum is read out from the memory to limit the rate of opening of the recirculation rate regulating valve.