| 摘要 |
A method and apparatus for monitoring deterioration of an internal combustion engine exhaust gas purifier in which first and second sensors are disposed on the upstream and downstream sides respectively of the purifier. The sensors are connected to an electronic control unit which, in normal operation, is arranged to control the air-fuel mixture supplied to each cylinder of the engine by controlling the amount of fuel supplied by an injector so that the air-fuel ratio is a predetermined mean value. The air-fuel ratio is changed from one predetermined value to another predetermined value and delay time taken for the second sensor to change its response subsequent to said change is indicative of the condition of the purifier so that deterioration of the purifier may be readily determined.
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