Patent ID: 7487035
Filing Date: 2009-02-03
Classification: F02D

Abstract:
1. A cylinder abnormality diagnosis apparatus of an internal combustion engine, comprising: an air-fuel ratio sensor for detecting an air-fuel ratio of exhaust gas which is disposed in an exhaust confluent portion where the exhaust gases from a plurality of cylinders of the internal combustion engine merge with each other; an air-fuel ratio estimation means for performing a cylinder air-fuel ratio estimation of estimating an air-fuel ratio of each cylinder based on a detection value of the air-fuel ratio sensor; an abnormality diagnosis means for performing a cylinder abnormality diagnosis of determining whether each cylinder is abnormal based on an estimate result of the cylinder air-fuel ratio estimation; and a determination means for determining whether or not an operating state of the internal combustion engine is within a specified operating range in which an estimate accuracy of the cylinder air-fuel ratio estimation increases, wherein when it is determined by the determination means that the operating state of the internal combustion engine is within the specified operating range, the abnormality diagnosis means performs the cylinder abnormality diagnosis.