| 摘要 |
PURPOSE:To solve abnormality early and prevent the increase of harmful components in exhaust gas by opening or closing a sub intake passage forcibly at the time of a particular operating condition, and generating a signal of abnormality based on the detection value of a detection means at the time of changing over an opening or closing condition. CONSTITUTION:To promote the atomization of fuel from fuel injection valves 5 during warming-up operation, a sub intake passage 6 is opened by energizing a solenoid valve 9 when engine cooling water temperature is less than approx. 40 deg.C, so that auxiliary air is supplied to the periphery of the nozzles of the respective fuel injection valves 5. When engine cooling water temperature is over approx. 80 deg.C, a neutral and idling conditions are kept and engine speed is stable, auxiliary air is supplied by opening a sub intake passage 6 for prescribed seconds, the engine speed increases. At this time, for example, when one of branch passages 6a is clogged, auxiliary air is not supplied, so the increase in engine speed is restrained. It is thus possible to generate a signal of abnormality when maximum engine speed in prescribed seconds for which the sub intake passage 6 is opened is less than a preset one. |
