Abnormality-diagnosing device for evaporation purge system and air-fuel

Abstract

An abnormality-diagnosing device for an evaporation purge system and an air-fuel ratio controller for an internal combustion engine having the abnormality-diagnosing device incorporated therein, which device can: prevent misdiagnosis as abnormal, which otherwise would occur under the influence of evaporative fuel caused by altitude, or change or swinging of fuel level or fuel; prevent deviation of an air-fuel ratio from a target value during purging of the evaporative fuel, which otherwise would occur under influence of the evaporative fuel resulting from altitude or fuel level; and, prevent deviation of the air-fuel ratio from the target value when the purge valve is opened, whereby a failure in drivability or aggravation of harmful exhaust component values can be prevented when the evaporative fuel is purged. The abnormality-diagnosing device includes a control device whereby, when a purge amount accumulation value exceeds an abnormality diagnosis start purge amount accumulation-determining value after start-up of the engine, then control is executed to diagnose at least one of an internal tank pressure sensor and an atmosphere valve as abnormal when an internal tank pressure does not reach any value between minimum and maximum internal tank pressure values with reference to atmospheric pressure in a state of the purge valve being closed and the atmosphere valve being opened.