| 摘要 |
PROBLEM TO BE SOLVED: To determine with accuracy a learned value for an air-fuel ratio and a learned value for evaporation when evaporative gas is to be supplied (purged) to a common air intake passageway in common to each cylinder group by providing an independent air-fuel ratio feedback control for each of a plurality of cylinder groups. SOLUTION: Air-fuel ratio feedback control is provided by using an O2 sensor 13L for a left bank 1L and an O2 sensor 13R for a right bank 1R. Evaporative gas is supplied from a canister 30 via a purge valve 35 to a common air intake passageway 3 shared by the right and left banks. When the purge valve 35 is closed, a learned air-fuel ratio is uniquely determined for each of the right and left banks based on an air-fuel ratio feedback correction value. When the purge valve 35 is open, a learned evaporation value is uniquely determined for each of the right and left banks based on the air-fuel ratio feedback correction value. The learned values for air-fuel ratio and evaporation are determined alternately. When the learned values for either air-fuel ratio or evaporation for both the right and left banks have been determined, those for the other are to be determined.
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