Air-fuel ratio control system for an internal combustion engine with an atmospheric pressure responsive correction operation

摘要

An air-fuel ratio control system for an internal combustion engine, including an oxygen concentration sensor producing an output signal whose level is substantially proportional to an oxygen concentration of the exhaust gas, effects a feedback control of the air- fuel ratio of mixture to be supplied to the engine toward a target value determined on the basis of various parameters of the engine operation and corrected in response to a magnitude of atmospheric pressure, so that the target air- fuel ratio is made lean as the magnitude of the atmospheric pressure decreases. Thus, the reduction of the engine output power and the increase of the fuel comsumption which have been encountered in conventional systems are prevented.