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Thread: P38A engine stalling at idle

  1. #1
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    P38A engine stalling at idle

    I have a 2000 4.6 P38A with 230kkms. It is dual fuel/LPG. It's blue

    It has been running and starting fine on both LPG and fuel for 6 months. In the last few weeks the cold idle has degraded to a point where it now idles dangerously low for a few seconds, surges occasionally and ultimately stalls a couple of times until it is warm unless I give it some throttle. This seems to happen on fuel and LPG. It is obviously noticable because I also start it (using key only, no throttle, every time I drive it and wait patiently for a minute or two before I drive it). ODBII shows no fault codes.

    I was thinking I would crack open the idle stepper and clean it out and also the throttle body and air inlet passages. Any other wise suggestions?

    I also flick quite often between LPG and fuel. Is this a bad thing? I am nervous of backfires popping my new MAF, so I never climb hills or overtake on LPG, but cruise on highways and around town no problems. Often I start and finish on LPG - maybe this is screwing the fuel maps?
    Now: 2005 L322 Vogue 4.4 M62TU (Black)
    Before: 2000 P38A HSE 4.6 - stately capability | 2008 Kluger KX-S | 2004 Forester | 2000 Yamaha XJR1300 | 1993 VR Calais | 1974 HQ Statesman - 308 V8 | HT | HK

  2. #2
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    I dont have gas.
    But i thought that the RR will/should start on Petrol warm upto 50c then switch over automatically to gas.
    Not sure if you have a non injected gas system?

    I had a similar problem with my idle some time ago so i replaced the TPS throttle position sensor.....no improvement.
    So i pulled the stepper motor out and it fell apart in my hands/ unrepairable it was.
    I got a new one fitted/ they have got a setting that requires them to be adjusted some how.
    Any how long story short i had some continuing idle problems/minor.
    I took it to a specialist LR w/shop and now she is fine.
    The stepper was original 14yrs old and i had 260k km on the clock.

    Could check your air filter ignition leads and your fuel filter under the drivers door.
    If you havnt done the fuel filter in a while i would look at this any way (watch the pressure in it if you take it off)

  3. #3
    drewandkate@iinet.net.au Guest

    PHOS

    We recently had a similar problem with our 1995 R.R HSE stalling at idle on the odd and becoming more frequent occasions.Our HSE has been gas injected for 700 hours and im not sure if it is related to the gas, but it has had stalling issues since the gas was fitted and not prior.I asked my mechanic mate what an idle speed motor does and mentioned my idle issues and he suggested we clean the throttle body and idle speed motor, so far no stalling.

  4. #4
    It'sNotWorthComplaining! Guest
    It could also be as simple as a vacuum hose coming off or leak at the rear of the motor, the one that goes from the throttle intake to the rear of engine.

  5. #5
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    i have the opposite problem with mine since the new engine, it idles at 1800rpm untill it warms up and then attempts to idle between 650 and 1100 (cam lope causing the warm problem).
    not very helpful i know but interested to try and nut it out.

  6. #6
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    I had that issue when my fuel pump was failing, and due to the low pressure in the fuel manifold, the engine was starving fuel. Having said that, the throttle positioning sensor can cause that and also a loose or faulty MAf sensor cable can cause this also. There is a way to test this by putting the MAF sensor into limp home mode. My mechanic did this, funnily enough it ran better than with the MAF sensor functioning. I'm not sure of the procedure on doing this, maybe someone else can shed some light on this method.

  7. #7
    jsp's Avatar
    jsp is offline Master Silver Subscriber
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    check the big orings in the air intake pipe are still in one piece or even there at all.....

    2007/2002/2000/1994/1993/1988/1987/1985/1984/1981/1979/1973 Range Rover 1986 Wadham Stringer
    and a Nissan Cube............
    South Australia.

  8. #8
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    I would tackle the simple stuff first before delving deeper.
    My '89 classic had idiling problems pretty much exactly as you described. I cleaned the throttle body with throttle body cleaner and guess what? Instant fix! Hope that's all it is for you.

  9. #9
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    I have recently had similar problem of low idle (on Gas only) after a little hot start backfire. Was there anything came of this as far as the fix for the original problem?

  10. #10
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    Glen

    Get the oxygen sensors checked. If they aren't right they can really mess with the engine. The gas system uses the readings.

    Ask me how I know that ....

    Dave
    2011 Range Rover Sport SDV6 Autobiography
    2007 Range Rover Sport TDV6
    2004 Freelander TD4 SE
    1997 Range Rover 4.6 HSE
    1994 Range Rover Vogue
    ----------------------------------------

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