INTER-CYLINDER AIR-FUEL RATIO IMBALANCE ABNORMALITY DETECTION DEVICE FOR MULTI-CYLINDER INTERNAL COMBUSTION ENGINE

PROBLEM TO BE SOLVED: To improve the accuracy of detecting an inter-cylinder air-fuel ratio imbalance abnormality and prevent wrong detection, in a multi-cylinder internal combustion engine capable of implementing ignition timing control for each cylinder.SOLUTION: In the deice in which abnormality detection processing (S103 to S105 and S107) of detecting the inter-cylinder air-fuel ratio imbalance abnormality on the basis of revolution speed fluctuations of the multi-cylinder internal combustion engine and ignition timing control for controlling the ignition timing so as to restrict revolution speed fluctuations in the multi-cylinder internal combustion engine are implemented, the implementation of the ignition timing control is restricted when the abnormality detection processing is implemented. It is possible to improve the detecting accuracy of the inter-cylinder air-fuel ratio imbalance abnormality and to prevent the wrong detection because reduction of the rotation fluctuation accompanying with the implementation of the ignition timing control is restricted.