| 摘要 |
PROBLEM TO BE SOLVED: To certainly judge respective conditions of deterioration of combustion in a plurality of fuel injection modes set on the basis of different target air-fuel ratios, by judging the deterioration of combustion in a manner that detected results of combustion fluctuation are judged according to a judged threshold value set separately, for each fuel injection mode. SOLUTION: When an engine 1 is operated, a target average effective pressure (load correlation value) is calculated in an ECU 70 on the basis of the output signals of a throttle opening sensor 29 and a crank angle sensor 17. Then, when judging deterioration of combustion, for example, an angle speedωand angle speed deviation dωare found out as evaluation values for the purpose of detecting combustion fluctuation (rotational fluctuation) in the engine 1. Then, a fuel injection mode set for the engine 1 is checked up on, and when judged that it is not a compression stroke injection mode or an intake stroke injection mode, but a stoichiometric injection mode, a judgment threshold value is found out by referring the map of the judgment threshold value concerning that mode, and when the angle speed deviation dωis larger than the judgment threshold value, it is judged as deterioration of combustion.
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