| 摘要 |
PURPOSE:To suppress the air-fuel ratio having an abnormal value when an exhaust concentration detection system is in trouble by keeping the coefficient value which varies according to the output of an exhaust concentration detector to the upper or the lower limit, when said coefficient value becomes over the upper limit or below the lower limit. CONSTITUTION:An air-fuel ratio controller controls the opening time of an injection valve 6 by obtaining in an ECU 5, the standard injection time from each output signal of a revolution number sensor 11 and an absolute pressure sensor 8 which detects the absolute pressure in an intake pipe 2 and by correcting said standard injection time by the constant and/or the coefficient in accordance with the operation parameters of an engine water temperature sensor 10 etc. Further, the air-fuel ratio is feedback-controlled by varying the above mentioned coefficients according to the output of an O2 sensor 15. In this case, if the coefficient value becomes over a prescribed upper limit, the coefficient value is kept at the upper limit, and when the coefficient value becomes below a prescribed lower limit, the coefficient value is kept at the lower limit, and thus the air-fuel ratio having an abnormal value can be avoided beforehand. |
