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New turbo fitted but losing power, feels restricted like air mass flow meter fault?

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by SMc, Apr 18, 2013.

  1. SMc
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    SMc Member

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    My turbo was on the way out with leaky seals so just had a recon turbo fitted. Car idles and revs ok when in neutral, but on the road it has a big flat spot between around 1500rpm and 3000rpm. If you try to accelerate from low revs it just doesnt go anywhere! once it gets past 3000revs the turbo seems to be spooling ok.

    It seems to be showing the characteristics of an air mass flow meter fault but the car was running perfectly before we changed the turbo.

    Just for the record, it was fitted by a good mechanic who has done many turbos before...we are both pretty sure everything is back where it was so struggling to find the fault. Any ideas?

    Oh, its a 2002 A4 Avant 1.9TDi Sport 130bhp.....

    Thanks in advance for the help....

    Cheers
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  2. HEKTOR
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    HEKTOR Member

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    Boost Leak or limp mode. Do you have access to vag com so you can check fault codes?
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  3. beachbuggy
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    beachbuggy Well-Known Member

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    wastegate issue, either not plumbed in properly or as its a recon unit not setup up correctly
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  4. adamss24
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    adamss24 Well-Known Member

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    The PD 130 engine uses a VNT turbo, there's no wastegate there. I would pay attention to the vacuum hoses as it's easy to knock them off and if there's a vacuum leak then the turbo wont boost properly. As hector mentioned, i would scan the engine for fault codes then take it from there...
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  5. SMc
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    SMc Member

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    Thanks guys....still not solved this. Mechanic has checked and pretty damn sure everything is on the way it should. The EGR valve was clogged so we changed that but it still drives the same.

    There are no fault codes to indicate exactly what's going on, he's got the diagnostic equipment.

    I should say, it's erratic the way it performs. If you accelerate fairly quickly from a standing start it seems to be ok in 1st and 2nd gear....and turbo spooling as it should....then when you are continue in 3rd it just kind of dies and wont accelerate more.

    We're going to try the air mass flow meter next but if its not that, I'm guessing beachbuggy may be right and its the recon turbo thats the problem :(
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  6. beachbuggy
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    beachbuggy Well-Known Member

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    I meant vnt, I did know, just typed the wrong thing:) too used to 1.8ts!
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  7. Slinepete
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    Slinepete Member

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    Not an audi but my impreza used to do this and it was because it was over boosting and hitting it's safety cut off not sure if its anything like on these cars but have you tried resetting the ecu and then building the boost up gradual in each gear allowing the ecu to learn the parameters,like I say not sure it's the Same on these cars but just a thought that may help
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  8. SMc
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    SMc Member

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    Ok...an update!

    We have now changed the air mass flow meter today and on the test drive, it immediately felt better. I felt there was still a slight bit of lag compared to the old turbo but at least it was consistent and drove in a 'normal' fashion. However, after a few miles of stop-start and open road driving I went on to the motorway and accelerated up into 5th and the car ran out of power....foot to the floor in 5th and it would not accelerate past 80mph. Came off the motorway and the car was back to the way it was....sluggish, incosistent, totally lacking power etc....

    So....we are back to square one. What's confusing is how the car ran apparently ok for the first 15miles or so after the air mass flow meter was replaced...but then suddenly slipped back into running like a plug again?

    This is driving us nuts!! Please can anyone help?
    Last edited: Apr 29, 2013
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  9. SMc
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    SMc Member

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    Bump....someone must have an idea? appreciate any help or suggestions....

    I have noticed a pattern......when you first pull away it drives close to normal...accelerates and boosts in every gear....but after the first minute or so, usually when hitting around 2500rpm in 3rd gear....the car nosedives and slips into what is like a limp mode....acceleration is then almost non-existent. But, stop the car and restart it...we have boost and 'normal' driving again....until 3rd gear and 2500rpm again....then into a limp mode again.

    Any ideas? Can this be a problem with the actual turbo itself? The car was running fine before we changed the turbo (albeit the turbo seals had gone and there was oil in the system).
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  10. SL11CKK
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    SL11CKK Active Member

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    Have you thought about returning the turbo and getting another unit. Have heard of recon unit messing about
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  11. SMc
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    SMc Member

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    No yet mate, need to eliminate everything else first as it will be a bit of a job!

    Another factor...my mate followed me and said under heavy acceleration...there is heavy black smoke coming out the exhaust.
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  12. Steffgj
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    Steffgj Member

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    This sounds very similar to what I'm experiencing at the moment. Only started a few days ago and have done absolutely nothing to the car recently.

    Going to start investigating this week and will post back if I find anything.
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  13. SMc
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    SMc Member

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    Likewise mate....I'll keep you posted on this thread how it goes for me and maybe it can help you ;)
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  14. Audi Doodah
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    Audi Doodah Active Member

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    Have you done some boost logs? Engine block 11 in vcds shows required and actual boost. Issues with the map or n75 would log a fault code though, I think.

    Otherwise, I think you have to admit the turbo is a fault. It's the only major part you've changed. Happens quite a lot in my job fixing military aircraft, believe it or not. Unserviceable on fit, we call it.
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  15. Paul B7
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    Paul B7 Active Member

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    I have had almost exactly the same issues as yourself. The diagnosis from my Indy is that the turbo vanes are sticking. I am fitting a new turbo tomorrow and would suggest you take your turbo back for a refund/exchange. Good Luck .
    #15
  16. BRILLO
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    BRILLO Member

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    did you ever get to the bottom of this
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