Weird lope in idle and lack of power when accelerating...

Discussion in 'Everything Technical' started by lite1979, Jun 21, 2016.

  1. lite1979

    lite1979 Printing Shit!

    2001 Audi TT 225 Quattro Coupe, 1.8t AMU block, almost 160k miles; mostly stock except for a 3" DP + high-flow cat, spaced-out rear O2 sensor, APR 93 Octane tune.

    My car acts like it's getting momentarily starved of fuel the past few days. I'll accelerate in gear, and it'll stop, then resume acceleration. When I let off the gas, the RPMs drop a lot faster than normal, and they'll drop to ~500, then jump back to 1100 before settling around 850, which is the normal idle speed for my car.

    I have no codes stored in the ECU, no CEL (obviously), and all other indicators (temp, fuel gauge, mpg) seem to be within normal specs. What should I be looking for?

    If it's a vacuum leak, it hasn't been consistent enough to give me a long-term fuel trim code, and I've had and fixed several vacuum leaks over my seven years of ownership, so I doubt that's the cause.

    Would a fuel filter cause these symptoms? How about a dirty MAF? Perhaps a dirty air filter?

    Help. I'm lost!
     
  2. vw to bimmer

    vw to bimmer The Krazy Professor

    I would do fuel filter to start ruling out possibilities. If it seems like its starving for fuel it just might be. When was it done last, if you don't remember do it!
     
  3. lite1979

    lite1979 Printing Shit!

    Fuel filter done, but I still have a problem. It's a serious lack of power when accelerating in boost.

    Idle is nice and steady. I really feel the lack of power when I'm around 2000-2500 rpms, or if cruising, while going from decelerating to accelerating in a higher gear.

    Seems like it could be a few things. I've never replaced the N75, though I'm not familiar with the symptoms of a failing one. I think it could also be something like the wastegate actuator.

    Is there a vacuum leak on the 1.8t that would not cause a CEL?
     
  4. A4 Deja vu

    A4 Deja vu Posting- God

    Check ur readings on ur maf sensor with vagcom.
     
  5. A4 Deja vu

    A4 Deja vu Posting- God

    U can check ur waste gate by applying air pressure to it only needs like 5 psi to move unless it's broken inside which I've seen more then once
     
  6. lorge1989

    lorge1989 Posting- God

    How old are you coils? You could have a weak one that fires fine when idling, but in boost it could struggle. I guess that would probably throw a code tho.
     
  7. lite1979

    lite1979 Printing Shit!

    I've never checked MAF readings before w/VAG-COM, but I can do it from inside my garage, right?

    Also, a quick scan of the engine gave me this:

    Address 01: Engine Labels: 06A-906-032-AMU.lbl
    Control Module Part Number: 8N0 906 018 K
    Component and/or Version: 1.8L R4/5VT G 0003
    Software Coding: 06710
    Work Shop Code: WSC 06701
    Additional Info: TRUWT28N711021023 AUZ5Z0Y9303044
    VCID: 397330FC23946EF679-5141
    5 Faults Found:

    16795 - Secondary Air Injection System
    P0411 - 35-10 - Incorrect Flow Detected - Intermittent
    18058 - Powertrain Data Bus
    P1650 - 35-10 - Missing Message from Instrument Cluster - Intermittent
    16684 - Random/Multiple Cylinder Misfire Detected
    P0300 - 35-10 - - Intermittent
    16685 - Cylinder 1
    P0301 - 35-10 - Misfire Detected - Intermittent
    16514 - Oxygen (Lambda) Sensor B1 S1
    P0130 - 35-10 - Malfunction in Circuit - Intermittent

    Readiness: N/A
     
  8. lite1979

    lite1979 Printing Shit!

    In response to your question about the ignition coils, they are almost four years old. All Beru brand from GermanAutoParts. I put a new one onto cylinder one after getting that code, but it persisted. I then changed the spark plug, and it hasn't come back since. I replaced the other three spark plugs as well.
     
  9. lite1979

    lite1979 Printing Shit!

    It's about time I practiced some VCDS-fu skills anyway. Anyone want to help me? I've never checked for misfires while driving, for example, and I don't think it's legal to do so.
     
  10. A4 Deja vu

    A4 Deja vu Posting- God

  11. lite1979

    lite1979 Printing Shit!

    I'm familiar with every vacuum line in this car. I didn't hook any up backwards (or touch any vacuum lines before this started happening, which is why I'm so stumped). Secondary air is fixed. I broke a line when I changed my spark plugs.

    I'm going to log MAF reading and misfires today if I can. Thanks!
     
  12. lite1979

    lite1979 Printing Shit!

    So I checked out blocks 15 and 16 to count misfires, and though I had single digit misfires on nearly every cylinder, they would all reset to zero eventually. This did not coincide with the hesitation (or the stalling I got when observing from idle - I stalled when I first started the car, then three more times after I went out for my drive.

    I look at 002, 003 and 006 to figure out if the MAF was the culprit, but I'm not sure I know what I'm doing with that. Is 25% the maximum adjustment for the front O2? Because I saw that frequently while observing in my driveway and just pressing the gas pedal. It was hesitating pretty badly.
     
  13. lorge1989

    lorge1989 Posting- God

    Maybe unplug the MAF and drive around, see if its better. If reverting back to a preset map helps, I would think the MAF or a vacuum leak post maf could be your culprit.
     
  14. lite1979

    lite1979 Printing Shit!

    Done and done. MAF it is! I drove from my house in North Buffalo to my credit union near the corner of Main and Chippewa downtown with the MAF unplugged, and the car drove great (slightly underpowered, but no hesitation or hunting idle).

    Now, who's got the best price on a new MAF for an AMU 1.8t?
     
    Last edited: Jun 27, 2016
    RoachinRay likes this.
  15. A4 Deja vu

    A4 Deja vu Posting- God

    Boom and boom it will be underpowered I would stick with an oem do u have a part number?
     
  16. lorge1989

    lorge1989 Posting- God

    Still could be a vacuum leak haha, but trying cleaning it. My JSW was doing some funky stuff, I cleaned the MAF it was good. And I also can check my stash of MAFS I might have one too.
     
  17. lite1979

    lite1979 Printing Shit!

    Part# is 06A906461E according to ECS. Jason at Black Forest has a good price on a new one, but feel free to search and let me know what you find!
     
  18. lite1979

    lite1979 Printing Shit!

    At this point, if it were a vacuum leak, I would have gotten at the very least a soft code for long term fuel trim, and I haven't, so I'm counting on a new MAF to get me running again. Of course this has to happen the week I'm moving my girlfriend into my house, and I'm broke because of it. Once I collect rent and utility money I should be able to afford a new one.
     
  19. lite1979

    lite1979 Printing Shit!

    Ok. I'm totally stumped now. Jason Dale gave me a great price on a new MAF. I just installed it, and the car is still running like garbage with the MAF plugged in.

    Also, it is way too hot out to be working on cars today...

    Edit: When it cools down, I'm going to check the vacuum lines going to the brake booster, and any other vacuum line that may have a check valve in it. I have a feeling that's why I never got a CEL for the unmetered air...
     
    Last edited: Jul 7, 2016
  20. lite1979

    lite1979 Printing Shit!

    The good news is that

    1. I now have code p1136 (which means the new MAF is doing its job)

    2. I found a vacuum leak right where the vacuum line meets the brake booster. I'll update this thread with my results.
     
    lorge1989 likes this.

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