| 摘要 |
PROBLEM TO BE SOLVED: To improve the accuracy of the abnormality determination of an exhaust emission recirculation device even in a state that an oxygen occlusion capacity of a catalyst is lowered.SOLUTION: In a step S102, an air-fuel ratio inclination ΔAFR_ON in the execution of EGR is corrected so that the air-fuel ratio inclination ΔAFR_ON is increased with respect to a decrease of a maximum oxygen occlusion amount Cmax of an exhaust emission purification catalyst 24. In a step S103, an air-fuel ratio inclination ΔAFR_C in the execution of EGR which is corrected in the step S102 is further corrected by an air-fuel ratio inclination ΔAFR_OFF in the non-execution of EGR. In a step S104, block abnormalities of per-cylinder EGR ports 23-1 to 23-4 are determined by comparing an air-fuel ratio inclination ΔAFR_INB in the execution of EGR which is corrected in the steps S102, S103 with an allowable limit value ΔAFR_LIM.SELECTED DRAWING: Figure 4 |
