| 摘要 |
When a wastegate valve, which opens and closes an exhaust bypass passage bypassing an exhaust turbine, is open, exhaust gases of respective cylinders bypass the exhaust turbine and pass a sensing point of an air-fuel ratio sensor downstream of the exhaust turbine. Accordingly, the exhaust gases of the respective cylinders can be avoided from being mixed by the exhaust turbine, so an influence of an inter-cylinder variation in an air-fuel ratio due to an inter-cylinder imbalance abnormality becomes apt to appear in an output waveform of the air-fuel ratio sensor. Therefore, existence or nonexistence of the inter-cylinder imbalance abnormality is determined based on the output of the air-fuel ratio sensor when the wastegate valve is open. Eventually, the existence or nonexistence of the inter-cylinder imbalance abnormality can be determined accurately, thereby improving detection accuracy of the inter-cylinder imbalance abnormality.
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