05 Passat TDI wagon intermittent acceleration problem

Discussion in 'VW Mk4 Jetta, Golf, New Beetle, Passat TDI forum' started by smh6nn, Sep 25, 2013.

  1. smh6nn

    smh6nn New Member

    Joined:
    Sep 25, 2013
    Messages:
    3
    Car:
    2005 Passat TDI Wagon
    I own a 2005 Passat TDI wagon and for the past three months we've had a intermittent problem with accelerating. The problem usually occurs when trying to pull out on a main highway near our home. The car will struggle to accelerate to 30-40 mph, it's a 55 mph highway, and even with the accelerator pressed to the floor the car will not be able to climb above 40 mph. The problem has always gone away after parking the car and turning it off. Next time out the car runs fine with no acceleration issues. We took it to the local VW dealer and they replaced the turbo. Within days the problem recurred. We took it back and they replaced the valve leading to the turbo, or at least that's my understanding of the part they replaced. Within a week the same issue came up again. I took the car back to the dealer and they've now had the car for 10 days and I was just told they cannot find anything wrong. Said they are having their senior tech drive it home and night and they've found the issue very intermittent and no error codes are triggered. He said they've also done fuel pressure testing and found nothing wrong and they do not think there's anything wrong with the transmission. I have spent more than $3k replacing the turbo and valve and the problem still exists. My wife no longer is willing to drive the car with our kids since it's a really safety hazard when the problem happens and you cannot accelerate beyond 40 mph. A friend suggested this might be a good forum to get some possible explanations of what is wrong. Thanks in advance for any suggestions.
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  2. NewWestTDI

    NewWestTDI Member

    Joined:
    Feb 9, 2013
    Messages:
    142
    Car:
    2005 Passat TDI GLS
    Location:
    Hamilton, ON
    Mods:
    Eibach Pro/Koni FSD | Dai Status 18x9 | Michelin Pilot Sport AS3 235/40/18 | Black Halos | Colt Stage 2 | BS Delete | Custom Lower Grilles | 750W Monsoon
    First of all welcome to the MTD forum! There's a lot of great resources here so you've come to the right place.

    It sounds like your car is going into "limp mode". That usually means that it won't accelerate much past 45-50mph due to the ECM cutting power to the engine at higher speeds as a fail safe due to a problem. If it was a bad turbo (compressor not spinning at all due to worn bearing) it wouldn't be intermittent, it would be low power all the time. So it seems the dealership replaced your turbo unnecessarily. I would have thought the VNT actuator was a possibility but they replaced that as well and it didn't fix the problem. I suggest removing your car without having anymore work done there. It's unfortunate when shops replace things as a way of troubleshooting. When they road tested it did they exceed 40 mph? highway test? Do you get any smoke from the tailpipe especially when accelerating? Are there any noises like a whooshing sound or hissing?

    So if you can provide any more details it would be helpful. My intuition is telling me that maybe you have a boost (or possible vacuum) leak. The lower turbo hose is prone to developing a leak due to the ground wire rubbing on it. You can either do a boost leak test or just have the engine running while listening and feeling for an air leak from under the hood, around the turbo. Caution, it gets hot in there. Do it when the engine is cold. If the leak is just starting then it won't necessarily produce any engine codes but there should be some black smoke on acceleration. Take it for a drive and have somebody follow you and put the pedal down hard to allow them to see if there's any puffs of black smoke. The other possibility is a vacuum leak in the hose leading to the VNT actuator or the cannister, unless the dealership replaced any of those as well?

    There are other reasons for limp mode but they'd produce engine codes so one step at a time. The low power is one safety issue, however these vehicles have another safety issue as well that needs to be addressed so it's best not to drive it until these things can be addressed. Read this link especially the part about oil pump noise:

    http://www.myturbodiesel.com/1000q/b5/vw-passat-TDI-buying-guide.htm


    welcometomyturbodies
    Last edited by a moderator: Sep 25, 2013
  3. smh6nn

    smh6nn New Member

    Joined:
    Sep 25, 2013
    Messages:
    3
    Car:
    2005 Passat TDI Wagon
    Additional information

    Thank you for the reply. There is a great deal of black smoke when you press the accelerator for fast acceleration. I was told that would be the case for some time after the new turbo was put in but it's been more than a month.
  4. NewWestTDI

    NewWestTDI Member

    Joined:
    Feb 9, 2013
    Messages:
    142
    Car:
    2005 Passat TDI GLS
    Location:
    Hamilton, ON
    Mods:
    Eibach Pro/Koni FSD | Dai Status 18x9 | Michelin Pilot Sport AS3 235/40/18 | Black Halos | Colt Stage 2 | BS Delete | Custom Lower Grilles | 750W Monsoon
    No problem. Well, with a new turbo there shouldn't be any black smoke really. Black smoke means a rich air/fuel mixture = too much fuel because not enough air. A new turbo should be compressing sufficient air into the intake so that doesn't make sense. Since you still have limp mode, the black smoke then is likely due to an air (boost) leak and it's most likely at the lower turbo hose connecting to the intercooler piping. You can get at it from under the vehicle by jacking it up and removing the splash guard. If you need step by step I can help with that. I don't recommend going to the dealer for a new hose because it's over $400 for the hose only and then there's labour and they don't need anymore of your hard earned $$.

    Here is a link to purchase it online:

    http://www.metalmanparts.com/product.sc?productId=559&categoryId=63

    But first make 100% sure the hose itself is leaking by listening for air leakage with a cold engine. It could also be that the hose has come loose from the connections at either end and it might be as simple as reattaching it properly. The clips that connect this hose at both ends tend to come loose or don't secure the hose properly. You can spray soapy water around this hose (easier from underneath) and have someone press the throttle a few times gently and look for bubbles or just listen for hissing or whooshing sounds. It's really easy to replace. Just make sure the connections at both ends are secured tightly.

    Cheers
  5. smh6nn

    smh6nn New Member

    Joined:
    Sep 25, 2013
    Messages:
    3
    Car:
    2005 Passat TDI Wagon
    Thank you again

    Thank you once again. As soon as I get the vehicle back I will use your suggestions to see if I can find the issue. I am very grateful to now have an idea as to what is going on.
  6. chrismk5

    chrismk5 Member

    Joined:
    Sep 17, 2013
    Messages:
    123
    Car:
    mk5 golf 1.9 tdi 105ps bkc
    Location:
    Durham uk
    Mods:
    gt tdi injectors pipercross panel filter remap
    Was the turbo accuator set to factory when installed this could cause a few issues, lack of boost,too much boost
    Wrong fuel air ratios etc,

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