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Leon TDI ALH 90hp - loss of power

Discussion in 'Engine Discussion and Tuning (archive)' started by przemek.czekaj, Oct 13, 2011.

  1. Hi all,

    I was wondering if you could help me to find the root cause of my problem. The thing is that when revving the car on the 3rd gear onwards I can feel a loss of power at some point (under higher load) and the car stops accelerating linearly.

    I have carried out some dynamic test using VAG-COM and recorded logs.

    The results point at faulty MAF sensor, however I am not too sure. Apparently with MAF disconnected the car should run better, it does not happen in my case. On the contrary, it behaves as if there was no turbo fitted when I disconnect the MAF sensor.
    Yesterday I cleaned the sensor with a specific spray (CRC MAF cleaner), it didn't help.

    Also, there is a mismatch in Specified and Actual value in turbo boost (block 11), but I am not too sure if the difference is worrying, or maybe it is caused by this faulty MAF.

    I am open to any suggestions and advice.

    Thanks for helping me out. I cant post this logs here unfortunately :(
     
  2. Seatmann

    Seatmann Rough around the edges

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  3. Random1989

    Random1989 FR MAD

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    90bhp i agree!!

    you tried the simple things ? airfilter? boost leak ?
     
  4. Thanks for quick responses. I will try this MAF test later on.

    The airfilter is brand new and I dont hear any worrying noice of escaping air to be honest. How would you recommend investigating it though? Are there any specific spots prone to failure? Thanks
     
  5. Seatmann

    Seatmann Rough around the edges

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  6. Random1989

    Random1989 FR MAD

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    egr valve ?
     
  7. Seatmann

    Seatmann Rough around the edges

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    Your user name suits you lol but yeh, it's a rare one but the egr valve can cause it too right enough.
     
  8. Thanks, so EGR is the first one to dismantle and clean. Will do that tomorrow probably. Of course you will be the first ones to know the results. Cheers
     
  9. Seatmann

    Seatmann Rough around the edges

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    Have you tested the maf yet? It's fairly quick and easy to try.
     
  10. sssstew

    sssstew Editing your spelling

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    so you say the results point to a faulty MAF, how come? what have you seen?

    If when you unplug the MAF the performance stays the same or not much different then you know the MAF is dead. The difference between plugged in and not should be night and day. A good MAF, when plugged in will make the engine powerful and pull strongly (assuming no other issues), if you then unplug this good MAF then the performance drop should be hugely noticable, if when you unplug the MAF you dont notice much difference then you know your MAF is dead.

    So what you state above is right :-

    "On the contrary, it behaves as if there was no turbo fitted when I disconnect the MAF sensor. "

    This is how it should be if you unplug it, as the ECU reverts back to default values for air flow and fueling which are on the safe side, so little performance.
     
  11. Seatmann

    Seatmann Rough around the edges

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    You'd think so but from all I've read it doesn't seem to be that way for everyone and the only real test is using vagcom/vcds. Sometimes a maf can be bad but not completely shot so the car can be down on power but disconnecting the maf might show it to be very different and make you think it's ok when in fact it isn't.
     
  12. Muttley

    Muttley Catch that diesel!

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    ALH engines have a VNT turbo. I expect this is sticky vanes. EGR valve would be the next most likely. Doesn't sound like MAF to me.
     
  13. Seatmann

    Seatmann Rough around the edges

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    Yeh but start with the simple stuff though eh? And we don't know if there's any specific codes or wether it's actually going into limp mode or if the power is coming and going etc

    Not enough details, need more details.
     

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