| 摘要 |
PURPOSE:To make it possible to compensate the air-fuel ratio with respect to secular changes, by changing the amount of secondary air so that the compensating amount of the air-fuel ratio is determined in accordance with the amount of secondary air which is obtained when a signal from an O2 sensor indicates the stoichometric air-fuel ratio. CONSTITUTION:During running of the engine 1, a computer 19 receives the outputs of various sensors 7, 15 through 18, detects the running condition of the engine, and refers to the relationship between the air-fuel ratio and the amount of air, corresponding to an engine running condition previously stored in a memory. Further, if the relationship between the engine running condition and the amount of secondary air at that time does not coincide with the previously stored one, the compensating control is initiated since the air-fuel ratio is out of a predetermined value. That is, an air selector valve 9 is controlled to be opened and closed so that secondary air from an air pump 13 is fed into an exhaust pipe 4 through a supply passage 11, and the compensating amount of the air-fuel ratio is determined in accordance with the amount of secondary air which is obtained from the level of an air-amount sensing unit 16 when a signal from an O2 sensor 15 indicates the stoichometric air-fuel ratio. |
