Trouble diagnostics for air-fuel ratio control system

Abstract

Abstract PURPOSE:To prevent a wrong diagnosis from occurring, by closing an evaporated fuel purge controlling on-off valve as long as the specified time at a time when an air-fuel ratio feedback quantity reaches the upper limit value and, when the relatively small feedback quantity temporarily set at this time reached the upper limit value, having it judged to be trouble occurrence. CONSTITUTION:At the time of engine driving, whether an engine driving state satisfies a condition for a trouble diagnosis or not is judged at an electronic control unit 41. Here, in the case where it is judged 'yes', the purge controlling on-off valve 28 installed in an evaporated fuel purge passage 27 connecting an evaporated fuel suction device 22 to a suction passage 12, is closed as long as the specified time when an air-fuel ratio feedback quantity reaches the upper limit value in substance. And, simultaneously with this valve closing operation, the feedback quantity is temporarily set to the specified value smaller than the upper limit value. And, after that, when the feedback quantity is substantially reached to the upper limit value, it is so judged that an air-fuel ratio control system gets out of order.

Inventors

• 👤 Fumiaki Asano
• 👤 浅野　史明
• 👤 Nobuki Uchitani
• 👤 内谷　信喜
• 👤 Miki Otsuka
• 👤 大塚　幹
• 👤 Masahiko Noba
• 👤 野場　正彦

Bibliographic Details