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2.0 TDi Not Holding Boost

Discussion in 'A3/S3/Sportback (8P Chassis)' started by APL TDi, Mar 2, 2009.

  1. APL TDi
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    APL TDi Member

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    [Mar 2, 2009]
    Hi all

    My 2004 2.0tdi 140 was remapped on saturday.

    The original rr said it was only making 126bhp and after the fast road map it as making 155bhp.

    The guys at chip n spin said it was not holding boost. So they run it in 5th gear to make it boost and got 163bhp (sttill not great).

    It had a recon turbo fitted about a month ago, and for about a week afterwards it would stutter under acceleration. Then it all seemed fine until yesterday.

    Does anyone have any ideas what would cause it not to hold boost?

    Cheers
    #1
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  3. A_C4mby
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    A_C4mby Member

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    [Mar 2, 2009]
    Do you have VCDS(VagCom)? A few logs might find the problem?

    Where in the UK are you?

    Without investigating I could say:

    1. Large boost leak - but you should hear it.
    2. Sticking actuator.
    3. Vacuum pipe not connected to actuator.
    4. Blocked CAT/Exhaust?
    5. Vac not being switched on to actuator.

    Just a guess!
    #2
  4. Oli.
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    Oli. Member

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    [Mar 2, 2009]
    Air flow meter is common as hell on these engines!
    #3
  5. APL TDi
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    APL TDi Member

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    [Mar 2, 2009]
    Cheers lads

    I am hoping its not a sticking actuator as it is a newley reconditioned turbo.

    I live in Guildford (about 30 miles south of London)

    I have suspected a boost leak for quite a while, but I recon the guys at chip n spin would have picked up on that?

    I am gonna get it back on some rollers this week hopefully and have a good look under the car.

    Would a faulty air flow meter cause it to underboost?
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  6. Oli.
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    Oli. Member

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    [Mar 2, 2009]
    And the air flow meter won't throw up a fault code - What will happen with the car is the turbo will cut in then die off again, almost immediately. Every VAG TDI engine that I've had, I've replaced this on them.

    Just my tuppence, and only £60 or so for a new one
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  7. A_C4mby
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    A_C4mby Member

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    [Mar 2, 2009]
    Yeah, I've had a faulty MAF as well.

    A good check is to just unplug the MAF and see if it improves, the engine will use and estimated MAF signal when it is unplugged.

    If can feels like new when unplugged, then you've found your baby!
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  8. APL TDi
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    APL TDi Member

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    [Mar 2, 2009]
    right I am off to do that! lol

    bbs!
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  9. APL TDi
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    APL TDi Member

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    [Mar 2, 2009]
    Right oh

    Just took it out for a spin, got it hot, did a few fast runs on a road near me first to give me a datum. Then unplugged the MAF and did the same runs. Once I unplugged the MAF the car ran like a dog, did not seem to get any boost at all.

    Sounding more like a hose on the actuator or the actuator its self.

    What is the easiest way to get to the turbo? Through the top or underneath?

    I am guessing if its through the top the pipe at the back of the engine needs to come off?
    #8
  10. A_C4mby
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    A_C4mby Member

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    [Mar 2, 2009]
    I'll try unplugging my MAF at lunchtime.

    It was a number of years ago when I had a MAF problem (I put a 130 PD TDI engine into a corrado!).

    The best way to get at the turbo is from underneath, but you have to remove the undertray.

    The vacuum hose is clipped to the turbo intake hose from the MAF sensor down o the turbo.
    #9
  11. APL TDi
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    APL TDi Member

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    [Mar 2, 2009]
    Cheers for that info on the vac hose mate!
    It probably would have taken my 30mins to work that out
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  12. APL TDi
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    APL TDi Member

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    [Mar 2, 2009]
    Well im going to give it a ruddy good service, put some red-x in it and put it back on some rollers Friday.

    Its a bit odd but it seemed to go like a rocket today compared to saturday??

    I guess time will tell...

    Cheers for all the imput
    #11

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