Patent ID: 7721591
Filing Date: 2010-05-25
Classification: F02D,Y02T

Abstract:
1. An abnormality diagnosis apparatus for an internal combustion engine comprising: an air-fuel ratio sensor provided in a confluent portion of exhaust gas discharged from each cylinder of the internal combustion engine, and detecting air-fuel ratio of the exhaust gas; an information detecting means for estimating an air-fuel ratio of each cylinder or a deviation in the air-fuel ratio between the cylinders based on an output of the air-fuel ratio sensor while an air-fuel-ratio dither control is performed for compulsorily varying the air-fuel ratio of each cylinder by a predetermined variation in a rich direction or a lean direction; and an abnormality determination means for determining that an abnormality occurs in a specified cylinder when a number of times in which the air-fuel ratio of the specified cylinder estimated by the information detecting means or the deviation in the air-fuel ratio of the specified cylinder exceeds a decision value is greater than a predetermined number.