Air-fuel ratio control system for internal combustion engines.

摘要

An air-fuel ratio control system for an internal combustion engine controls the air-fuel ratio of a mixture supplied to the engine to a desired air-fuel ratio in response to an output from an exhaust gas ingredient concentration sensor. A first value of the desired air-fuel ratio is calculated (S7) based on the rotational speed of the engine and the load on the engine. A second value of the desired air-fuel ratio is calculated (S8) based on results of determination of whether a vehicle on which the engine is installed has just started from a standing position thereof. A third value of the desired air-fuel ratio is calculated (S9) based on results of determination of whether the temperature of the engine is lower than a predetermined value. The largest value of at least the first to third values of the desired air-fuel ratio is set to a final value of the desired air-fuel ratio. <IMAGE>