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Thread: 3.9 V8 high idle between gear shifts

  1. #1
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    3.9 V8 high idle between gear shifts

    Hi all

    I had a few problems with my 3.9 Disco, mainly rich running and erratic idle. After a search on here I cleaned the stepper motor, the MAF (which was filthy) and hit all the sensor connections with contact cleaner. The rich running has cured and it settles down to idle quite nicely now. When shifting between gears however, the idle stays around 1500rpm. It drops down after a few seconds. I've checked throughly for air leaks. Where else should I be looking?

  2. #2
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    hi mate, check the throttle linkages/springs and cable on the inlet manifold, my discovery was doing the same thing and i found them to be dry and not returning properly, bit of grease spray sorted it out

  3. #3
    Boony73 Guest
    How old are your leads, plugs, rotor and cap? also do a search on the site for Bee utey's bim024 upgrade, it may not solve your problem but it certainly won't hurt and your economy may improve.

  4. #4
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    The idle should stay up at about 1100 in neutral if the car is moving, so it will do that.
    Most people don't notice but once you notice you become OBSESSED.

    This is programmed into most injected cars. In an auto it is to smooth the change down to first when stopping, but several manuals I have had have done the same thing. Probably for emissions.

    AFAIK the signals to ECU are revs under 1500 so injectors on, signal from VSS, and TPS less than .49 volts. IE idling when moving.
    Regards Philip A

  5. #5
    Roverlord off road spares is offline AT REST
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    May be the TPS is sticking, have you cleaned the inside of the throttle throat and TPS.


  6. #6
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    I lubed up all the linkages and cleaned out the throat and TPS. Seems to only do it now for the first km or two until it warms up a bit. Running beautifully otherwise!! Loving the V8 versus the Tdi

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