Please Help, 2002 Jetta TDI limp mode

Discussion in 'VW Mk4 Jetta, Golf, New Beetle, Passat TDI forum' started by Kris Brown, Mar 9, 2017.

  1. Kris Brown

    Kris Brown New Member

    Joined:
    Mar 9, 2017
    Messages:
    3
    Car:
    2002 VW Jetta TDI
    Location:
    Indiana
    So, I'm working on a 2002 Jetta TDI, stock, automatic. My friend bought it at an auction. The transmission was shot. We rebuilt the transmission and it shifts great now. But, we then discovered NO BOOST. The turbo actuator was shot. We replaced the acuator and vacuum line and the turbo started spooling(the rod moved freely and didn't bind up). We then had an overboost code. So, we ordered a new N75 solenoid from the dealer. The car still went into overboost, and limp mode (low power, wouldn't rev over 3200). It also popped a egr Flow code. After digging through the threads we found a common link of clogged intakes. We removed the intake and hot tanked it for two days. I cleaned the egr out and everything looked great. We re-assembled everything and fired it up. The throttle response was better than ever. But when you crowd the throttle it goes into low power limp mode. Toggle the key off and back on and everything is normal until you get into the gas. At idle the turbo is sitting at 1010mbar. It has three codes pending.

    Overboost
    Egr flow
    Manifold pressure high.

    I'm loosing my mind here. I've looked through threads and couldn't find anything new. Hopefully I've posted this in the right area. Please forgive me if I haven't, I don't really post in groups.
     
  2. Kris Brown

    Kris Brown New Member

    Joined:
    Mar 9, 2017
    Messages:
    3
    Car:
    2002 VW Jetta TDI
    Location:
    Indiana
    The problem has been found. It was two issues.

    1st, the adjustment rod on the turbo actuator was out of adjustment.

    2nd, the check valve that is at the vacuum pump was clogged with crud. It was the smaller line that feeds the solenoids. I cleaned it out and the car drove out great...well as great as an automatic can.
     
    Tdieezi likes this.
  3. Ted Tolentino

    Ted Tolentino New Member

    Joined:
    Sep 4, 2016
    Messages:
    7
    Car:
    Jetta, TDI, 2002; Passat, v-6, 2002
    Location:
    Oklahoma City
    Hi Kris, I have the exact same model and year Jetta as you describe. And yes, I am experiencing limp mode now where the vehicle will not accelerate when entering the freeway ("highway", depending in which part of the country we are speaking), tail exhaust black, and the transmission won't shift up until well over 2.3 to 2.5 thousand RPM. No CELs. Knowing now what was wrong with your vehicle, and assuming my problem has a similar if not exactly the same cause as on your vehicle, would you suggest a different order of diagnosis and/or parts replacement as you did to help solve my problem. I am just not sure where to start the process. I have read the write-up on "Limp Mode" diagnosis on this forum but your description seems closer to what I am experiencing than the general or global explanation given in the write up. Thanks for your time.
     
  4. Oldaccord

    Oldaccord Active Member

    Joined:
    Jan 11, 2014
    Messages:
    661
    Car:
    1998 Beetle TDI
    Location:
    BC, Canada
    Ted, you have to start somewhere, so start with this!
    1st, Check your rod adjustment then if all is good, check your vac system!
     
  5. Kris Brown

    Kris Brown New Member

    Joined:
    Mar 9, 2017
    Messages:
    3
    Car:
    2002 VW Jetta TDI
    Location:
    Indiana
    Ted, I actually had Codes kick the light on. I had overboost and a egr flow code. Here's what I would recommend if I had to start over. First, do you hear the turbo at all? If not, I would remove the vacuum line from the N75 solenoid that goes toward the turbo actuator. Put a mighty vac on it and see if: a) it holds a vacuum, b) the rod moves. If it holds vacuum but doesn't move the rod I'd unhook the the rod from the turbo and and try again. The arm on the turbo should move freely. If it doesn't hold vacuum I'd plug straight onto the actuator itself. If it still doesn't move I'd replace it, the vacuum line, and I'd go ahead and replace the N75 while I'm at it. Make sure to adjust the rod properly if you replace the actuator. If they all check good, put your mighty vac at the vacuum pump, start the car and see if it builds vacuum. If it does start following the lines out checking in along the way.

    If the turbo and actuator are good.

    I'd pull the tube off of the intake on the passengers side and look into the egr to see how bad the buildup is. I've read the VW allows 4mm of build up max. It wasn't the cause of my limp mode, but cleaning the intake did really improve throttle response. It took about 2 hours to get it apart, an hour to clean the egr housing, a couple days in a hot tank for the intake, and about 2.5 hours to re-assemble. The difference made it worth doing. Parts cost $20 or so.

    Basically, I would
    Troubleshoot as much as possible without just throwing money at it. I was surprised these parts cost more than BMW parts.

    I would also put a scan tool on it. If it has a "pending" code it won't pop the light. Hope this helps, let me know if I can help anymore.
     
  6. Ted Tolentino

    Ted Tolentino New Member

    Joined:
    Sep 4, 2016
    Messages:
    7
    Car:
    Jetta, TDI, 2002; Passat, v-6, 2002
    Location:
    Oklahoma City
    Kris and Oldaccord, thank you both for the suggestions. I'll plan on getting a start on the Jetta in the morning and report back how I fared. Much gratitude to you both.
     

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