Air-fuel ratio control system for automotive engines

Claim 1

An air-fuel ration control system for an automotive engine, said engine having a canister for purging fuel vapor from a fuel tank from the canister to an intake passage of said engine, an O 2 -sensor for detecting oxygen concentration of exhaust gases of said engine and for producing a corresponding voltage signal, a feedback control system responsive to said voltage signal for producing a coefficient as a function of said voltage signal for controlling air-fuel ratio of air-fuel mixture induced into said intake passage of said engine, and a fuel injection control system for calculating amount of fuel by an equation including said coefficient to inject a proper amount of said fuel in dependency on driving conditions of said engine, the improvement of the air-fuel ratio control system which comprises: detector means for detecting when the fuel vapor stops purging from said canister to the intake passage and for producing a purge cut-off signal when said detector means detects the stopping of said purging of the fuel vapor; and correcting means responsive to said purge cut-off signal for simultaneously stopping the controlling of the air-fuel ratio via said feedback control system by setting said coefficient to 1.0, thereby preventing said engine from malfunctioning when the fuel vapor stops purging.