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Power problems with 1996 A4 110hp TDI AFN

Discussion in 'A4/S4 forum(B5 Chassis)' started by ollied1981, Nov 8, 2006.

  1. ollied1981
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    ollied1981 New Member

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    Just joined the forum to ask a question...hope someone can help!

    Have had the car about 6 months, no problems until a few days ago when i noticed sometimes it's not pulling right....putting my foot down it felt like a flat diesel - it's most noticable in second and third where you usually accelerate hardest. There's no smoke, oil loss or unusual noises, it's just as if there's no boost. Strangley if i hold the accelerator down eventually it seems to rev through it and pull ok.

    This started off as an intermittent fault a few days ago but now it seems to be all the time...i'm guessing this means it's not a mechanical problem with the turbo since then it just would_not_spin.......

    I've checked the fault codes with vag-com, non were recorded. I've had someone rev it up, both the egr valve and the actuator on top of the turbo move, although the one on the turbo felt as though the movement was a bit 'sticky'. Does this car have the variable vane turbo rather than a wastegate?

    Oh yeah, i've just replaced the maf sensor since this seems to be the usual suspect and it's made no difference :(

    Any suggestions greatly appreciated!

    Oliver

    **update...ok on the way home it went completely flat and wouldn't rev through it at all...but when i pulled over, turned if off and restarted it pulled properly all the way home....**
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  2. inigoj
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    inigoj Member

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    I had the same problem with my 97 A4 TDI 110 (afn)

    If you have replaced your Pierburg maf (7.18221.01.0 or 7.18221.51.0, some joker on ebay tried to sell me a VW T4 Transporter maf ending .58.0) the next most likely suspects are the N75 valve (pressure converter for boost control at the front of the engine near the turbo, it has a grey top and connects to the top of the turbo. Pierburg part no: 7.21903.70.0 for your car)

    Or a leak in one of the small bore tubes relating to turbo management/intercooler hose/small tube to ecu.

    Or your inlet manifold is choked up because of the EGR, and is not allowing enough airflow.

    Or sticking VNT actuator (finding a quiet road and reving its tits off can loosen it)

    Curiously my 3000rpm overboost problem went away when i added a cheap tuning box, pulls like a train to approx 4800rpm.

    There is some useful info on checking your maf and n75 here:

    http://www.msi-motor-service.com/ximages/PG_SI_0017_EN_WEB.pdf
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  3. inigoj
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    inigoj Member

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    Could also be your EGR valve or its N75 controller malfunctioning (near bulkhead on an afn).

    They can make a 'squawking' noise if they are malfunctioning due to resonance. Or just not close or open properly.

    I pulled the vac hose off mine and sealed it with a bolt. Seemed to gain a bit of power too.
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