Air/fuel ratio control system having function of controlling supply of secondary air into intake pipe of internal combustion engine

摘要

An air/fuel ratio control system for performing feedback control of the air/fuel ratio of an air/fuel mixture being supplied to an internal combustion engine in response to the concentration of an exhaust gas ingredient. The air/fuel ratio control system includes a device for controlling a shot air valve for supplying secondary air into the intake pipe of the engine. The control device is connected to a solenoid valve for controlling the shot air valve and operable to open the solenoid valve to hold the shot air valve inoperative for a predetermined period of time after the engine rpm has increased across a predetermined value which is higher than the engine cranking rpm but lower than the engine idling rpm, to thereby prevent misfire within engine cylinders at the start of the engine.