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Thread: Help! Too much boost now...what did I do??

  1. #1
    Garrett booster
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    Help! Too much boost now...what did I do??

    Bone stock '86 Turbo Z

    Boost gauge has always topped out just over 7 psi


    It sat outside during the brutal cold temps that we've had the last couple months. I got in to start it a couple days ago, and I had no brakes (never had a brake issue with it before). I pull it in (carefully, lol) the garage and determined that the master cylinder had died. So I put a new master cylinder on it, and decide to go ahead and put a new valve cover gasket on it too. Brake work goes silky smooth. With the valve cover off, I notice 3 busted vacuum lines (the hard plastic ones that are in a group of 4, run along the backside of the valve cover, and all go to the same vacuum fitting. I fix those and find no other issues. Valve cover back on, and all is good. On test drive, all seems great. Then I decide to lean on it a good bit, and as it was climbing, it cut out.....I think wtf, what was that? Drive it around town, runs perfect. On the long stretch country road headed home, I decide to see if I can duplicate the cut out. Come to stop, ease into it, then put the pedal 3/4 down in first, no issues and I see boost gauge climb to 8 at 5k shift (seem to feel faster than normal). 2nd gear, same 5k shift but boost gauge at 10 (feels faster still), 3rd gear, mash the pedal and the boost gauge burries, cut out....I slow down and then manipulate the throttle now that I know what I'm looking for (but did not push it to the cut out anymore). The car acts like I removed a governor and it will go full spool with full throttle, but I didn't mess with anything besides the 4 vacuum lines, the timing belt cover, and the master cylinder/bleed brakes.

    Any thought?

  2. #2
    boostaholic
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    Re: Help! Too much boost now...what did I do??

    sound like maybe siting outside (like my car has been) i would look at the actual wastegate can or the swing valve rusted shut.. tripple check your vaccuum tubes.. the nickel 3/16 brake line works great to replae the fragile plastic tubing...and it easy to bend..

  3. #3
    Garrett booster
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    Re: Help! Too much boost now...what did I do??

    I pulled it back in last night and did a good look over of all the lines, and everything else that I touched.


    What I found......(not sure if this is the cause but is seems plausible) is that the far end valve cover gasket rubber rolled upon the install, leaving a roughly 3" gap between the valve cover and the head hump. I'm puling it back off today and correcting it. Would the loss of vacuum in the valve cover (as all the lines going to the waste gate are hooked up) create this?

  4. #4
    Supporting Member Turbo Mopar Contributor supercrackerbox's Avatar
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    Re: Help! Too much boost now...what did I do??

    Quote Originally Posted by Gtdhw View Post
    I pulled it back in last night and did a good look over of all the lines, and everything else that I touched.


    What I found......(not sure if this is the cause but is seems plausible) is that the far end valve cover gasket rubber rolled upon the install, leaving a roughly 3" gap between the valve cover and the head hump. I'm puling it back off today and correcting it. Would the loss of vacuum in the valve cover (as all the lines going to the waste gate are hooked up) create this?
    In a word, No. It sounds to me like you have some of the vacuum lines hooked up incorrectly, or the wastegate is stuck as mentioned above. The only vacuum applied to the valve cover is the PCV valve, the rest should feed off the intake manifold.

    First off, check your codes for a code 13, which will tell you if you have a significant vacuum leak. However that code should also give you a check engine light, so I'm guessing that's not the issue. From there, go over the lines very thoroughly, specifically the ones from the intake to the wastegate solenoid and back to the wastegate. That's the circuit that controlls your boost. Let us know what you find.

  5. #5
    Garrett booster
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    Re: Help! Too much boost now...what did I do??

    Quote Originally Posted by supercrackerbox View Post
    In a word, No. It sounds to me like you have some of the vacuum lines hooked up incorrectly, or the wastegate is stuck as mentioned above. The only vacuum applied to the valve cover is the PCV valve, the rest should feed off the intake manifold.

    First off, check your codes for a code 13, which will tell you if you have a significant vacuum leak. However that code should also give you a check engine light, so I'm guessing that's not the issue. From there, go over the lines very thoroughly, specifically the ones from the intake to the wastegate solenoid and back to the wastegate. That's the circuit that controlls your boost. Let us know what you find.
    [TABLE="class: postbit_tbl, width: 100%, align: center"][TR][TD="class: alt1, bgcolor: #FFFFFF"]No check engine light (and it does work)

    fixed valve cover gasket, no dice.

    It has to be something with the 4 vacuum lines (coming from the 4 into 1 fitting on the top of the intake manifold) and the three same size hoses running along the back of the valve cover (one of which I know goes to the wastegate). There were three broken hoses, all in the same general location, and I spliced them back together based on their lengths. The problem now, is that I can't find a hose diagram showing where the all go to on the solenoid rack so that I can know if/where I spliced them wrong...

    [/TD][/TR][/TABLE]
    Last edited by Gtdhw; 02-27-2014 at 04:21 PM.

  6. #6
    turbo addict
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    Re: Help! Too much boost now...what did I do??

    time to buy some new line and Tees. I use brass NPT fittings to replace the factory plastic stuff.

    the lines can take only so many years and so many heat cycles.
    1988 Lancer Shelby 2.2TII 1989 Shadow ES 2.5TI 1992 Lebaron Sedan 3.0Auto 1993 Acclaim 2.5TI-A520 Hoard parts now!

  7. #7
    boostaholic
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    Re: Help! Too much boost now...what did I do??

    Didn't someone at one point make a nice vacuum block and set up?

  8. #8
    turbo addict
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    Re: Help! Too much boost now...what did I do??

    I bet all the vendors do, its just bar stock drilled out with some NPS threaded holes. id imagine it would be of cnc quality. unlike my hax saw/ drill press job.
    1988 Lancer Shelby 2.2TII 1989 Shadow ES 2.5TI 1992 Lebaron Sedan 3.0Auto 1993 Acclaim 2.5TI-A520 Hoard parts now!

  9. #9
    Garrett booster
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    Re: Help! Too much boost now...what did I do??

    [TABLE="class: postbit_tbl, width: 100%, align: center"][TR][TD="class: alt1, bgcolor: #FFFFFF"]Problem fixed! The busted WG hose was also broke down in the harness, that was the problem. All new hoses, to everything, re loomed, runs like a champ, back at 7 psi.. Seems to idle smoother too.

    [/TD][/TR][/TABLE]

  10. #10
    Supporting Member Turbo Mopar Contributor supercrackerbox's Avatar
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    Re: Help! Too much boost now...what did I do??

    Good job. And for future reference, here's a copy of your vacuum diagram: http://www.thedodgegarage.com/turbo/turbo86.jpg

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