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Thread: XJ12HE Stalls at full throttle

  1. #1
    Junior Member
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    XJ12HE Stalls at full throttle

    I have a 1984 XJ Series III with a V12HE engine. Since I bought it several years ago it has this annoying problem: when driving and accelerating normally all is well, but if I give it full throttle the engine stalls. If I at that time release the gas the engine revs normally and I can drive on. So, most of the time the engine runs fine (I even got compliments for the engine running so smooth), but when I push 'the pedal to the metal' it dies on me. Strange thing: every once in a while it does not and accelerates as fast as it should.

    What can be the cause of this issue?

  2. #2
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    i would suggest fuel starvation of some sort

    the strange thing is, you probably have fuel pressure, but when the pedal is pressed you need pressure and flow, with a blocked fuel filter the flow will be restricted, i am not sure if you have a ' swirl pot ' like the XJS , as this also has a mesh filter which gets blocked, but when the car stops the debris falls away from the filter and all is fine again until you need power

    i would also suspect the fuel pumps , old and weak ? possibly

    BB
    currently driving
    1994 3.2S XJ40 in Morocco red and Doeskin/Ruby red interior since 2016
    1989 V12 XJS White with Mulberry interior since 2004
    2004 2.1 X-Type Platinum with Champagne Leather interior since 2012

    previously ,
    1999 V8 Sovereign in Seafrost with Oatmeal and Antelope interior 2009-2013

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  4. #3
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    Thanks for your suggestion. I should point out that there's no need to stop in order to keep the motor running, just releasing the gaspedal is enough. I then am able to accelerate again, just as long as I do it nice and slow. This problem only occurs when I suddenly give full throttle, as long as I do the same thing in a more 'relaxed' way the car accelerates fine.

    Filter as well as pump (I only have one) are renewed, injectors are all serviced, distributor cap/spark plugs/ht leads are all renewed as well. Engine runs fine and smooth, apart from this issue.

    Could this be caused by a faulty coil? Perhaps a vacuum leak? What puzzles me is that every once in a while the kickdown functions as it should.

  5. #4
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    Suggestions/tips anyone?

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