| 摘要 |
PURPOSE:To judge the malfunction of an oxygen sensor irrespective of any variation in a supply of vaporing fuel, by installing a controlling device setting a purge valve down to non operation at a time when detecting output of an air-fuel ratio sensor is continued as long as the specified time and fixed to the overrich side or the lean side and, what is more it fails to reverse. CONSTITUTION:An electronic controller 9 performs air-fuel ratio feedback control by each detecting signal out of an air flow meter 2, an oxygen sensor 4 or the like. At this time, when exceeding an idle range, boost pressure comes to more than the specified value, whereby a purge valve 21 is opened by the negative pressure, and vaporing fuel in a canister 16 is fed to a suction passage via a three-way solenoid valve 30. Now, if detecting output of the oxygen sensor 4 is fixed to the overrich side or the lean side as long as the specified time, a signal is outputted to the three-way solenoid valve 30 from the ECU9, setting the purge valve down to nonoperation. Therefore, any malfunction of the oxygen sensor is kudgeable irrespective of variations in a feeding state of the vaporing fuel. Accordingly, such a possibility that air-fuel ratio feedback control is stopped by mistake, though the oxygen sensor is normal, is avoidable. |
