| 摘要 |
An air-fuel ratio control method for an internal combustion engine having a plurality of cylinders divided into at least two cylinder groups, wherein when each of the cylinder groups is in a first predetermined operating condition, the air-fuel ratio of a mixture being supplied to the each cylinder group is controlled in a feedback manner responsive to the output of corresponding one of at least two exhaust gas ingredient concentration sensors arranged in respective ones of at least two exhaust passage divided portions connected to respective cylinder groups, while when the each cylinder group is in a second predetermined operating condition, the air-fuel ratio of the mixture is controlled in an open loop mode corresponding to the second predetermined operating condition. When one cylinder group shifts from the first predetermined operating condition to the second predetermined operating condition, or vice versa, the air-fuel ratio for the one cylinder group is continually controlled in a control manner corresponding to one of the first and second predetermined operating conditions in which the engine was operating before the shift, until all the other cylinder groups shift to the other operating condition in which the on e cylinder group is operating after the shift.
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