METHOD OF DETECTING TROUBLE ON EXHAUST GAS CONCENTRATION SENSOR SYSTEM IN METHOD OF FEEDBACK-CONTROLLING AIR-FUEL RATIO OF INTERNAL-COMBUSTION ENGINE

摘要

PURPOSE:To prevent worsening of operation, by a method wherein, based on a correlative relation between air-fuel ratio correcting factor values responding to O2 sensors mounted in plural exhaust gas passages divided at each cylinder group, a trouble on an O2 sensor system is detected. CONSTITUTION:In a V-type 6-cylinder engine, exhaust gas passages 3A and 3B are independently located at each of first and second cylinder groups 21-23 and 24-26, and an O2 sensor 16 is installed to a portion on the upper stream side of the three- dimensional catalyst of each of the exhaust gas passages 3A and 3B. A fuel injection valve 8, controlled at each cylinder group, is located to the suction port of each cylinder, and feedback control of a fuel injection amount is effected based in an air-fuel ratio correction factor value according to an output from the O2 sensor 16. In which case, from a corrective relation between air-fuel ratio correction factor values responding to the O2 sensor 16, i.e., a difference between two correction factor values, a trouble on an O2 sensor series is detected. During detection of a trouble, based on an average value of correction factors set during preceding loop control, open loop control is effected.