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Cause and solutions to v6 tdi revving to 3k

Discussion in 'A4/S4 forum(B5 Chassis)' started by boost-addict, Jul 12, 2013.

  1. boost-addict
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    boost-addict Member

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    Looking to buy a tdi. I like the 2.5 and found one that has two faults.

    First is it runs out of fuel at 1/4 tank which after some searching turnt iut the transfer pump could have packed up.

    Second is it stops reving at 3k
    No mention of if it revs at idle.

    Ive found so far
    Blocked cat can be the main factor
    Air in fuel line from t-peice
    Turbo vanes stuck
    Altitude/boost sensor faulty

    Is there any thing else
    And can it be fixed? I presume this a common problem on vag tdi engines?

    Im tempted by the lower price but dont want to be stuck sticking money in to something i may eventually not solve


    The seller says he dosnt want to take it to a garage in fear of a big bill. Altho id say he must know as even i would go to a garage or seek help in the dirst instance of me not finding a fault like vanes or a blocked cat.


    So what can i ask the seller to give me a better understanding. And if he has no clue can a problem like this become a costly one
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  2. PAULF
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    PAULF Active Member

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    You need to scan it.
    Most likely it will be an overboost, then it goes into limp mode.

    There are quite a few posts on this have a search on here but
    the faults you listed are the main ones.
    Try checking the turbo actuator is down with the engine off, then watch it when the engine starts. It should move up to the stop freely.
    If it doesn't move, check the boost hoses and the N75.
    If it does move, try moving it by hand and feel if it is sticky or rough. If it is, buy your can of mr muscle.

    You can see if air is getting in by looking at the clear fuel line and watching for bubbles - rev it a bit whilst looking
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  3. boost-addict
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    boost-addict Member

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    I have serched! And thats the info i found. So theres not anything else other then mentioned that can cause this fault?
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  4. PAULF
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    PAULF Active Member

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    On any electronic vehicle, any of the ECUs involved in fuel or propulsion can cause strange faults too.

    However, the faults listed above seem to be most likely - but you must scan for fault codes first.

    To try and second guess which of the aforementioned faults you have without seeing what the ECU has logged is a path to unnecessary time wasting and expense.
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  5. PAULF
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    PAULF Active Member

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    On the plus side, once you get a 2.5 (Q?) running well you will enjoy yourself!

    I average (over a couple of years) 40+ MPG on my 2.5TDI Quattro saloon and it also goes like stink when I want it to.
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  6. boost-addict
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    boost-addict Member

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    yer might see if hes price will come down, wants £600 currently
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