To enable diagnosis without mistakes by forcefully opening and closing assist air control valve a specified number of times through forced opening and closing switch command means, and measuring variation amount in mechanism operation parameters so that when conditions for said change amount are detected multiple times to be equal to or below a specified value, it is diagnosed as a functional abnormality.
An assist air passage 8, having an air control valve 10 interposed therein, which supplies a portion of the intake air taken from an assist air intake opening 9 downstream of an air flow meter 2 and upstream of a throttle valve 3 by pressure differences between upstream and downstream sides. The downstream side of the assist air passage 8 is connected in the area near an injection pore of a fuel injection valve 5. The assist air control valve 10 controls the opening and closing to supply assist air for atomization of injection fuel. In this case, when conditions are decreasing vehicle speed and fuel-cut active, an intake valve variation amount Δ PB is measured a predetermined number of times, for instance 3, and when ΔPB1 through ΔPB3 are less than a predetermined value A, devices such as an alarm light are lit to notify operators and other people of the abnormality.
FUJIMOTO MICHIYUKI
OTANI SEIICHI
SHIOBARA KATSUYOSHI
Next Patent: DIAGNOSTIC DEVICE FOR ASSIST AIR SUPPLY DEVICE