| 摘要 |
An internal combustion engine (1) includes a throttle valve (10) for adjusting an amount of air taken into the combustion chamber (2), a turbo-charger (15) for boosting air taken into the combustion chamber (2), a variable nozzle mechanism VN for adjusting a boost pressure generated by the turbo-charger (15), and ECU (30) for setting an air-fuel ratio so that the fuel-air mixture becomes lean within a range of a predetermined lean-burn allowable area. When the ECU (30) determines that the abnormality occurs in the variable nozzle mechanism VN, the lean-burn allowable area is reduced so that an amount of intake air during the execution of the lean-burn operation is less than an amount of intake air when the throttle valve (10) is fully open under the condition where the variable nozzle mechanism VN is set at a lower limit of a boost pressure adjustment range.
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