Method of controlling air-fuel ratio

摘要

There is disclosed a control of learning correction coefficient compensating an aging of the air flow meter and a high altitude of highlands where the motor vehicle travels. A lower limit for a altitude compensating learning correction coefficient FHAC is computed by use of the altitude compensating learning correction coefficient FHAC determined during idling of the engine. A feedback correction coefficient FAF is determined such that it gets greater as the air-fuel ratio becomes smaller than the stoichiometric level of air-fuel ratio and it gets smaller as the air-fuel ratio becomes greater than the stoichiometric level of air-fuel ratio. When the mean value FAFAV1 of the feedback correction coefficient FAF is equal to the predetermined value or more, the altitude compensating learning correction coefficient FHAC is increased. Whereas, the mean value FAFAV1 is less than the predetermined value, the altitude compensating learning correction coefficient FHAC is decreased. The altitude compensating learning correction coefficient FHAC is not exceeded the lower limit therefor.