Evaporative emission control system for internal combustion engines

摘要

An evaporative emission control system for an internal combustion engine has a purge control valve arranged in a purging passage connecting between a canister and an intake passage of the engine. The evaporative emission control system has a self-diagnosis function of determining whether the evaporative fuel emission control system is normal or abnormal from a change in a value of a parameter measured based on an output from an exhaust gas component concentration sensor arranged in an exhaust passage of the engine, which change is detected when the opening of the purge control value is changed, and a variation in pressure within the intake passage at a location downstream of a throttle valve arranged therein when the opening of the purge control valve is changed.