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Sluggish 855T Turbo 850 1994

posted by  rsmigel on  Tue May 31 14:08 CST 2016
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last visit: Thu Aug 11 21:30 CST 2011
[RELATED]

Wife's car just threw a "check engine" light on the highway and read as a P0171. No other codes stored and this the is first CEL I've seen on this car in years.

I drove the car and noticed very low turbo boost... only 1/4 of the way in the white scale (I've got another boost gage coming and will report back with a more accurate reading) Performance matches the gage: sluggish with little torque. Gage on vacuum side looks good, 3/4 to the far left on deceleration and 1/2 on idle.

EGR system was replaced 25K miles ago. All vacuum hoses were replaced at the same time. Mileage is 181K.

I popped the hood and checked the big turbo hoses and every vacuum hose I could trace without disassembly. Everything looked fine.

Drove car another 100 miles w/o CEL light coming on. Added a can of octane booster and saw no performance improvement.

The car burns no oil.

I have an ACTRON CP9575 ( https://actron.com/sites/default/files/0002-000-3106_cp9575_mnl_english.pdf )to use for further study if it will be of any help.

Suggestions???







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    Sluggish 855T Turbo 850 1994

    posted by  rsmigel on  Sat Jun 4 04:05 CST 2016
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    last visit: Thu Aug 11 21:30 CST 2011
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    Problem fixed!

    Last night I removed the Idle Control unit and all associated high pressure hosing at the top front of the engine and found that the big hose connection to the intake manifold had been poorly fitted to the intake where the bottom of the clamp, where it is difficult to see, was hanging over the trim edge of the hose. Apparently that's where it leaked since when I properly fitted the big hose back to the intake, the power instantly came back. Now the torque is there and the turbo gage is driven two-thirds into the white with 1st-2nd gear shifts driving the gage near 90%.

    Thanks all for your help!








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    Sluggish 855T Turbo 850 1994

    posted by  rsmigel on  Fri Jun 3 06:27 CST 2016
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    last visit: Thu Aug 11 21:30 CST 2011
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    Is is possible to manually drive the turbo to a max boost condition using a hand held vacuum pump while driving the car and running a long vacuum line through the driver's side window?








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    Sluggish 855T Turbo 850 1994

    posted by  KlausC on  Thu Jun 2 19:02 CST 2016
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    last visit: Fri Oct 24 10:15 CST 2014
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    "Check for a vacuum leak", at the intake manifold, is the first answer. Use the OBDI boxes for a better error check. A-2.

    Grab each one of the IC hoses and give them a twist. If one moves, tighten it. Also check at the throttle body, the intake hose must be tight. Check for cracks in the flexible parts of the IC tubing.

    It might eventually be the MAF. A cleaning might be in order.
    --
    Keeping it running is better than buying new








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      Sluggish 855T Turbo 850 1994

      posted by  rsmigel on  Thu Jun 2 21:12 CST 2016
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      last visit: Thu Aug 11 21:30 CST 2011
      [RELATED]

      Thx Klaus.

      How do I use the OBDI boxes for a better error check?

      I forgot to add that I did remove and clean the MAF sensor with MAF cleaner (no effect).







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        Sluggish 855T Turbo 850 1994

        posted by  KlausC on  Thu Jun 2 21:45 CST 2016
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        last visit: Fri Oct 24 10:15 CST 2014
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        Robert can help:

        https://www.youtube.com/watch?v=bfeiZxhJgxY

        But your code is a result of a gross vacuum leak.

        Did you check the vacuum line near cyl #1?

        The turbo could be the result of a leaking vacuum line at the turbo or the boost control.
        --
        Keeping it running is better than buying new








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          Sluggish 855T Turbo 850 1994

          posted by  rsmigel on  Fri Jun 3 06:25 CST 2016
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          last visit: Thu Aug 11 21:30 CST 2011
          [RELATED]

          All three vacuum lines lines running to/fro the Turbo Boost Control attached to the airbox were replaced with blue silicone and are in perfect shape. I just checked those a few days ago when I removed and tested the Boost Control Valve.








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          Sluggish 855T Turbo 850 1994

          posted by  rsmigel on  Fri Jun 3 06:23 CST 2016
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          last visit: Thu Aug 11 21:30 CST 2011
          [RELATED]

          Are there codes to be read under the hood that have not / can not be read using my Actron code reader from the in-cabin OBD port?

          I only read one code and cleared that using my reader. The car has been driven ~200 miles since then and the code has not reappeared.

          I need to check the vacuum line near cylinder #1. Thx for the tip!








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    Sluggish 855T Turbo 850 1994

    posted by  rsmigel on  Thu Jun 2 12:11 CST 2016
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    last visit: Thu Aug 11 21:30 CST 2011
    [RELATED]

    I tested the "Turbo Boost Pressure Valve" and it appears to be functioning properly with a 12V test signal.

    Now I need to check the high pressure hoses again.








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      Sluggish 855T Turbo 850 1994

      posted by  Erwin on  Thu Jun 2 15:00 CST 2016
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      last visit: Thu Oct 23 10:39 CST 2014
      [RELATED]

      Similar issue with my '95 855T a couple of times over 10 years ownership. Vacuum hoses aside, two things to check are the vacuum tree under the throttle bellcrank cover and the short hose between the IAC motor and throttle body. Here are a couple of pics of what I've found.

      The hose between the IAC motor and TB rotted due to oil.

      photo HPIM0739.jpg

      The vacuum tree rubs against the cover and wears a large hole.

      photo HPIM0095.jpg

      Also, does your cruise control work? If not, check the vacuum lines at the CC solenoid under the battery tray.

      Erwin








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        Sluggish 855T Turbo 850 1994

        posted by  KlausC on  Thu Jun 2 18:55 CST 2016
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        last visit: Fri Oct 24 10:15 CST 2014
        [RELATED]

        I remember that great find of yours! I haven't seen another one since.

        The CC has it's own vacuum system, not engine related.

        Thanks for the reminder.
        --
        Keeping it running is better than buying new







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