98 tdi turbo/wastegate problems

Discussion in 'General Diesel Discussion' started by Rbgjetta, Mar 26, 2012.

  1. Rbgjetta

    Rbgjetta New Member

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    Hi, I'm a new member and need help with a wastegate problem on my '98 jetta tdi. I bought the car about 3 months ago and it has 210,000 miles on it. When I bought it the check engine light was on, but it ran well except maybe a little sluggish. The code had something to do with insufficent air flow; the previous owner had shown me, but he couldn,t figure it out. Having had 3 diesels already (1 Navistar, 2 Cummins), I thought I could figure it out. After replacing the cat and muffler which were clogged, I discovered that the wastegate was not opperating. I removed the exhaust from the turbo and sprayed carb cleaner into the wastge area, and lubricated the outside of the wastegate shaft. I disconnected the blue hose and using an air nozzle at 20 psi actuated the waste gate. Then repeated this process until everything moved easily. Put everything back together and ran the car, and the wastegate still didn't move. Then, wondering if the wastegate regulator might be bad, I disconnected the red hose and actuated the wastegate with an air nozzle. It worked fine. I then checked to see if the nozzle on the turbo going into the red hose was clogged. It was fine. So, it would seem to me that I might have one of two problems. The turbo isn't producing enough pressure to move the wastegate, or the wastegate isn't working properly. Does anyone know have to test for this so that I only have to take the turbo off once? Also, I did notice a little oil in the charge line to the intercooler, but the car doesn't really use much oil. Thanks, Randy
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  2. Seatman

    Seatman Active Member

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    If the car's sluggish it's not a wastegate problem, it only opens to release excess boost, it sounds more like you're not getting enough boost in the first place. Have you got access to vagcom? I would test the maf with it. Your turbo is fairly bomb proof on those.

    http://www.myturbodiesel.com/1000q/multi/low-power-fix-TDI.htm
  3. Rbgjetta

    Rbgjetta New Member

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    I'll try the vag-com, I know someone with one. Would that explain why it runs better in cold weather? Could it be mis-calibrated?
  4. Seatman

    Seatman Active Member

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    They tend to have a bit more power in cold weather anyway because cold air is denser so you get more in. Does it make a big difference to your car?
  5. Rbgjetta

    Rbgjetta New Member

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    Yes it does. I got the car in January and it would accelerate what I though was ok up to about 3200 rpms (this is my first small diesel). I knew it should have accelerated beyond 3200, but thought it had something to do with boost: it felt like the pump defueled. When the temp got to 70 degrees, it lost allot of power. I'm a little confused about the wastegate. Bentley's test for the wastegate is to unplug the wastegate regulator, rev the engine, and if it is working properly, the wastegate will move. To me that suggests that the default setting is open. That said, I have also read on this forum of an over boost situation if the wastegate doesn't open. I haven't found a diagram of the turbo yet.
  6. Seatman

    Seatman Active Member

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    No the wastegate stays shut and uses pressure to open, you can try it with the actuator unplugged, the worst you'll get is limp mode from overboosting. I think bently must be talking about disconnecting the actuator rod from the actual wastegate itself :confused:

    Did you have a look through that link I posted?
    I really think it'll be something else causing the power problem, it's very rare for that turbo to cause any problems as they're such a simple design. They don't tend to get stuck and if they do you get overboost but a quick freeing of the wastegate sorts that out.

    More likely to be the maf or electrical or something along those lines, maybe the egr valve. Have you got vagcom? I think you could really use it about now.
  7. Rbgjetta

    Rbgjetta New Member

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    I went to autozone and had the codes read. P0380 which they said was a crank sensor: Bentley's says it's a glow plug/heater. circuit fault. P1550 which is charge pressure difference and both agree. P1549 which is wastegate bypass regulator open/short to ground and both agree. I have checked the hose to the ECM and the hose I'm the ECM. Both are ok. I have replaced the air filter with a K&N high flow. The only thing I haven't checked other than to see if it was full of oil is the intercooler. If the wastegate regulator valve is intermittent, would that mean an over boost situation?
  8. Seatman

    Seatman Active Member

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  9. Rbgjetta

    Rbgjetta New Member

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    I have checked the wiring harness going to N75 and it is fine. So I guess I need to find a N75 regulator. I'll let you know what I find out after I replace it. Thanks for all your help.
  10. Frank M

    Frank M Member

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    The N75 may be doing what it is supposed to do. If it gets a high signal signal it will lower the boost.
    It can get a high signal due to a number of reasons.
    Don't waste $75 only to find out it is doing the same thing with a new one.

    Do some diagnosis first it will pay off in the long run.
  11. Rbgjetta

    Rbgjetta New Member

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    I replaced the wastegate bypass regulator with no difference in performance. I ordered a vag-com from Ross-tech today so that I can better diagnos the problem. I'll let you know what I find out.
  12. Rbgjetta

    Rbgjetta New Member

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    I recieved a cable from Ross-tech. I deleted the fault codes and they didn't return. Yet, the car is still underpowered. With the help of my daughter, we went on a test run while measuring Maf and intake manifold pressure. During max acceleration, the specified Maf reached 850mg/str while the actual only reached 495 mg/str. The intakes manifold pressure at 450 my/str reached 1500 mbar. I know there is no exhaust restriction. So, if anyone has any ideas, I could use your help.
  13. Seatman

    Seatman Active Member

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    Sounds like the maf might be bad but I'm not 100% sure, I think it can also be caused by the egr valve. Have a look in the faq at the low power and also there's another link somewhere about other things that can cause limp mode. I know it's not limp mode but it might give some idea of things to look at.
  14. Rbgjetta

    Rbgjetta New Member

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    If it's the egr, that would mean it might be stuck open bleeding exhaust off the turbo. Is there a chart that would show me what the intake manifold pressure should be? The highest I could get it was about 1520 mbar. Does that sound low?
  15. Seatman

    Seatman Active Member

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    Now that's something I don't know lol but someone else might.
  16. chittychittybangbang

    chittychittybangbang Administrator

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    don't think there's any charts but if you hold the mouse over the measuring block a tip box will appear. I forget if the bar is absolute or just above atmos. since 1 bar is standard pressure at sea level.
  17. Rbgjetta

    Rbgjetta New Member

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    So, today I rented a borrowed a vacuum pump from Autozone and tested the Egr valve which worked perfect. It even held when I left pressure on it. I did notice allot of oil residue in the intake pipe and manifold. Is this normal? My next option is to replace the Maf and see what happens. I'll let you know. Thanks for all the info.
  18. Rbgjetta

    Rbgjetta New Member

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    So, a friend of mine has a new MAF sensor which we tried whisks it did not help. I unplugged the intercooler and pressure tested it. It was fine. I still have the problem of a low MAF reading which has to mean there is a restriction in the system. I have replaced everything on the exhaust side of the turbo and checked every thing on the intake side of the turbo. Which leads me to think it's the turbo. I have noticed a film of oil on the piping from the turbo to the intercooler and back to the intake manifold. Does anyone have a good test for a turbo?
  19. Seatman

    Seatman Active Member

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    The film of oil is normal, it comes from the ccv (crank case breather)
  20. rexhooligan

    rexhooligan New Member

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    Hi, sorry to butt in, but I am also having an issue with low/no boost. VNT moves freely, replaced vnt actuator(was bad, had rust/dirt falling out of "weep hole"), vacuum hoses and egr solenoid. Also new air filter(stock) and fuel filter. Was running great then on way home from work, maybe 10-12 miles ,get off highway and start off from stop and no boost. Swapped the vacuum solenoids and ran great for a couple of days. Now same no boost after trip home. I was using my buddy's generic code reader and had maf numbers up but didn't know what I was looking for. Do I need to vagcom to see the actual vs spec numbers? I also noted before the solenoid swap that it didn't matter if engine warm or cold for no boost. Where should I go with this? I'm leaning towards maf but seems like it wouldn't be an on off thing but a gradual loss. Thanks

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