What causes F.I. engine to suddenly heitate off idle and idle poorly?

Discussion in 'Motorbike Technical Discussion' started by Dave, Oct 11, 2005.

  1. Dave

    Dave Guest

    I have a 2001 MV Agusta with low miles. I was doing some maint. on it this
    weekend (oil change, installed FBF risers, replaced ram-air-tube seal). I
    took it out to wash it after completing the work, and it didn't seem to run
    right. After washing it, I took it around the block and there was definately
    something wrong.

    The bike idles too low (maybe 600-700rpm), stalls at idle, and opening the
    throttle doesn't change RPM until it "catches" at some point, and screams to
    4-5K. It didn't have any of these symptoms when I last rode it about a week

    Someone suggested a vacuum leak, so I hookd ut my mercury-sicks and it all
    looks balanced. When I toll on the throttle in neutral off idle, the RPMs do
    not increase, but the vacuum drops? I checked out most of the sensors going
    to the CPU and they are at least close to right resistance.

    Any Ideas?

    1) Vacuum Leak: can't hear it, carb balance looks reasonable
    2) Fuel Filter or Pump: Bike seems OK at high RPM but won't idle well - my
    understanding is that if one of these was bad, the problem would be more
    pronounced at high enginer speeds, where more fuel is needed.
    3) Throttle Position sensor: This seems plausible. I disconnected it and the
    bike would idle but not accellerate at all, so some similarity there.
    Dave, Oct 11, 2005
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  2. Water inside the TPS, shorting it out, tricking the ECU into "thinking"
    that the
    throttle is open when it's not, so the ECU reduces the dwell time on
    the injectors?

    What about an O2 sensor? Got one of them? Maybe you got water or dirt
    into the
    vents on the O2 sensor. A hot oxygen sensor compares O2 in the
    atmosphere to O2 in the exhaust gasses...

    Maybe a plugged up O2 sensor is telling the ECU that you are trying to
    run your engine at 15000 feet above sea level, and again, the ECU
    reduces injector dwell time.

    But, doesn't the ECU run the FI in the open loop mode when engine
    temperature is low? Maybe you got water into the temperature sensor
    krusty kritter, Oct 11, 2005
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