| 摘要 |
PURPOSE:To aim at increasing the opportunities of failure discrimination by temporarily interrupting the purge of fuel steam when the feedback correction quantity exceeds the fixed critical value by continuing for a certain period of time so as to discriminate the failure of the air-fuel ratio control group and further resuming the purge. CONSTITUTION:An air-fuel ratio control device 102 feedback controls the air-fuel ratio on the basis of the output of an air-fuel ratio sensor. When the feedback correction quantity exceeds the preset critical value after the continuation for a certain period of time, the purge of fuel steam executed by means of a purge device 101 is temporarily interrupted through a purge control means 104 by the command of an interruption command means 103, and the failure diagnosis of the air-fuel ratio control group is executed by means of a failure diagnosis means 105. The purge control means 104 interrupts the purge temporarily and resumes the purge after the passing of the necessary time for the failure discrimination. The opportunity of failure discrimination in a running vehicle can be thus enlarged while preventing wrong diagnosis. |
