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Thread: p38 diesel lack of power

  1. #1
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    Default p38 diesel lack of power

    hi
    have just bought a p38 diesel manual g box
    it has an intermittent lack of power.
    its had: new fuel pipes,air filter,fuel filter,in-tank pump
    there are no fault codes on the dash its has been plugged in to lap top
    i have not yet driven it.........any idea's what it could be?

    thanks
    ps i am collecting it tomorrow....if i can drive it i will...if not the RAC will be getting a call

  2. #2
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    Default Re: p38 diesel lack of power

    hi
    update:
    it has no egr or maf
    it seems to be ok when cold.....but as soon as its warm...its undriveable zero power,but stays running...revs up ok hot or cold when not under load.turbo is boosting well.
    has had the air suspension removed and steel fitted.has asr manual on dash when you start it. has no other msg's on dash.
    does not rattle/knock/chuck out black smoke...........ticks over fine...had it ticking over for 20 mins......coolant gauge in the dash does not work.

  3. #3
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    Default Re: p38 diesel lack of power

    There is a small vacuum pipe what runs off the map sensor(side of diesel filter) and runs under the inlet maniofd,as that come off.

  4. #4
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    Default Re: p38 diesel lack of power

    rousecapri your p38 diesel does have a map sensor as speedy has said check the pipe going between it and the manifold but if the pipe was off you would have bad power all the time. my biggest concern would be coolant gauge not working , when the p38 gets too hot they will shut back in power you would pass one out on a bicycle. until they get hot they will perform beautifully. i would be asking if the dash is somehow bust and sending a corrupt signal or is there a sensor not working, or has the the person selling it tampered with it to hide a bigger problem like head gaskett blowing or a cracked head. check the expansion tank with the cap off for bubbles,and with the cap on when hot check if it is building too much pressure in the pipes(careful when checking pipes with enging running the fan is very near your fingers)

  5. #5
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    Default Re: p38 diesel lack of power

    sorted................i delved a bit deeper.(am a time served hgv mechanic and don't give up easily) the temp gauge turned out to be the wrong sender unit fitted........the diesel's have two wires going to the temp sender....green which is the 5volt from the becm/gauge and a brown/yellow....this wire does nothing....just sits in the loom going nowhere.........the sender that had been fitted.....did not earth out through the body...it needed the 2nd wire going to earth......works perfect now...........strange.
    the stat was changed...........while i was there i pulled the water pump......................impeller had come off...........so with the non working gauge and water pump..the second temp sender(for the engine ecu) must have been shutting the engine down to "save" it after a few miles................i will know for sure in the next couple of days once she is taxed...so i road test her fully.........

  6. #6
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    Default Re: p38 diesel lack of power

    that is exactly what is was doing if the vehicle thinks its overheating it will kill power so bad you couldnt pull the skin off a sausage. the impeller has a habit of spinning on the shaft and coming off. hopefully it hasnt overheated and done damage ................best of luck...............

  7. #7
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    Default Re: p38 diesel lack of power

    have done about 6 miles...round the block and had her running for about an hour.............she seems ok................i might have got lucky........only paid 625 for her so if the engine turned out to be dead i can soon put another lump in....

  8. #8
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    Default Re: p38 diesel lack of power

    they are a very easy engine to change any 2.5 bmw engine out of a bmw/omega will do

  9. #9
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    Default Re: p38 diesel lack of power

    have done nearly 200 miles in her now....................no issues.............. all it was then was the water pump

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