AIR-FUEL RATIO FEEDBACK CONTROL METHOD FOR INTERNAL COMBUSTION ENGINE

PURPOSE:To provide admissibility for difference in the altitude by comparing the sensed value of the exhaust gas concentration with the regerence value, and by setting this reference value according to the atmospheric pressure in case the air-fuel ratio of the mixture gas is fed back to the target air-fuel ratio in accordance with this result from comparison. CONSTITUTION:In an internal combustion engine 1, a throttle body 3 and a fuel injection valve 6 are mounted on a suction pipe 2, and a three-dimensional catalyst 14 is installed on an exhaust pipe 13. This exhaust pipe 13 is equipped with an O2 sensor 15 upstream the mentioned three-dimensional catalyst 14. An electronic control unit 5 compares the exhaust gas concentration sensed by this O2 sensor 15 with a certain reference value and feedback controls the air fuel ratio of the mixture gas to the target air-fuel ratio according to this result from comparison. Further the electronic control unit 5 is connected with an atmospheric pressure sensor 16. Setting of reference value is made in accordance with the atmospheric pressure sensed by the atmospheric pressure sensor 16.