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A4 1.9 TDI Motorway Speed Limp Mode

inigoj Jan 22, 2007

  1. inigoj

    inigoj Member

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    Recently my 97 A4 TDI 110 has started to go into limp mode when accelerating over 80mph.

    There are no problems accelerating uphill etc at lower speeds, just seems to be 5th gear?

    I have just been checking all the hoses and found that the small diameter tube from the inlet manifold to ECU pressure sensor was full of liquid. Could this affect anything?

    I have already changed my maf and boost N75.
     
  2. Caesium

    Caesium My BM is fixed! VCDS Map User

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    If the engine went into limp you'd only be able to do about 15-20mph.
    the liquid in this tube, what was it? whatever it was, its certainly not right.
     
  3. inigoj

    inigoj Member

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    When i say 'limp mode' i mean it is overboosting and shutting off the turbo.

    It will still accelerate but just as a non-turbo lump.

    Cycling ignition does reset it.
     
  4. Mcgough

    Mcgough Member

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    yea my last 130 Q did this when accelerating past 100mph, at exactly 100 it would go into limp mode,

    it went back to audi several times, they changed the Maf, the valve, then re-programmed Ecu, finally replaced Ecu, then eventually found the vane was sticking open on turbo, so they replaced it had no bother after that.

    you still under warrenty??
     
  5. Caesium

    Caesium My BM is fixed! VCDS Map User

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    Do you mean Wastegate?
     
  6. Mcgough

    Mcgough Member

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    ?????i got told Turbo Vane?? thats audi for you make special names up
     
  7. mattc83

    mattc83 New Member

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    the tdi have a varable vain turbo. bascally it is little flaps in the exshaust section of the turbo. they move to alter the angle of flow on turbine blades to reduce turbo lag
     
  8. Mcgough

    Mcgough Member

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    .......thats the little buggers!!
     
  9. Caesium

    Caesium My BM is fixed! VCDS Map User

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    I have seen what you mean now, they're lots of small vanes that adjust angle to control flow of exhaust gas onto the turbine blades. This technology does not need a wastgate.

    I'll hold up my hands and say I have never seen this in a turbo, but then again I've only ever had the turbo on a petrol engine apart, and apparently this technology is rare on petrol.

    See here http://www.autozine.org/technical_school/engine/tech_engine_3.htm#VTG
     
  10. inigoj

    inigoj Member

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    After towing a car on a very heavy twin axle trailer 500 miles today, my overboosting problem has vanished.

    Infact my car seems more powerful than it did when i first bought it, accelerates well, right through to 5k, pedal to the metal in every gear.

    Does this mean that the problem was a sticky VNT mechanism?
     
  11. Mcgough

    Mcgough Member

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    ...possibly. but possibly not apparently mine was sticking in the max/open position which made the car overboost while changing from 4th to 5th.

    possibly you had a diff problem which, now with a bit of italian tune, you have rectified!!!
     

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