Air-fuel ratio control method for internal combustion engines for vehicles

摘要

In an air-fuel ratio control method for electronically controlling the air-fuel ratio of a mixture being supplied to an internal combustion engine for a vehicle in response to operating conditions of the engine, a predetermined value of a parameter indicative of loads on the engine is set which corresponds at least to a detected value of a parameter indicative of the gear position of the transmission of the vehicle, and when a detected value of the engine load parameter is smaller than the set predetermined value, leaning of the mixture is effected. As the detected value of the above gear position parameter indicates a lower speed gear position, the above predetermined value of the above engine load parameter is set to a smaller value. Preferably, the predetermined value of the engine load parameter is set to a value also correponding to a detected value of engine temperature and/or a detected value of engine speed, in addition to a detected value of the gear position parameter.