INTER-CYLINDER AIR-FUEL RATIO VARIATION ABNORMALITY DETECTION APPARATUS

摘要

An apparatus according to the present invention includes a control apparatus configured to detect inter-cylinder air-fuel ratio variation abnormality based on a parameter correlated with the degree of a fluctuation in output from the air-fuel ratio sensor. The control apparatus is configured to execute a step of identifying two cylinders estimated to have a deviation of the air-fuel ratio based on an output waveform from the air-fuel ratio sensor during one engine cycle, a step of performing reducing control to reduce the deviation of the air-fuel ratio on each of the two cylinders, that is, a first cylinder and a second cylinder, to calculate first and second values of the parameter, respectively, and a step of identifying one of the two cylinders having the most significant deviation of the air-fuel ratio based on the first and second values.