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Thread: 0 PSI sutter/weirdness

  1. #1

    0 PSI sutter/weirdness

    UPDATE: Problem was intermittent. Ended up retuning at KT Motoring and it's been perfect ever since. Sorry no other solution to report.

    - - -

    I have an Evo 9 here tuned on Speed Density 10k+ miles ago. I just wanted to know if there's something else I should look at to diagnose this issue:

    At part throttle, at 0 PSI when the car goes from vacuum to boost it sometimes gets really jerky and fails to build boost.

    However, if I floor it past that threshold then the car builds boost perfectly fine. It's just that 0 PSI zone that's been acting up in the last few weeks. Immediately after this happens the car is unable to hold a steady idle and has even died twice. Restarting the car is usually fine and it'll drive perfect afterwards.

    I've tried installing the softer yellow spring for the Synapse DV and switched push/pull/ports. I got rid of part-throttle flutter, however the 0 PSI stutter thing is still an issue.

    Any ideas what I should be looking at? Two months before this started I got a rebuilt TB from Mil.Spec. I made sure that the throttle position sensor reads 13.3 in Evoscan. I also adjusted the BISS screw to 1.5 turns from closed.

    Boost leak test seems fine, holds about 25 PSI. Vacuum reads -15 at idle. Any other ideas? Some kind of very slow boost leak in a sensitive place? Clogged injectors? Spoolinup COP issues? Seems like braking hard after stuttering is a guaranteed way to make it die, so some kind of invisible brakebooster hole?

    Plugs look fine, here they are in order 1-4:




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    Last edited by another name user; 12-10-2014 at 06:52 PM.

  2. #2
    SoCalEvo.net Shop


    Mike W's Avatar
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    What turbo is it using? Sounds like compressor surge. Some of that can be possibly dealt with MIVEC tuning. But most would be the turbo sizing.

    Mike W

  3. #3
    Sorry for the wall of text, but this is at low RPM at part throttle cruising. It's a BBK-B BB with the anti-surge cover too.

    Other things I'll try to test: Spark plug coils, IAT sensor on the UICP, my imagination.

  4. #4
    Canyon Racer evo_jfa's Avatar
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    subscribed. I want to know final diagnose

  5. #5
    SoCalEvo.net Shop


    Mike W's Avatar
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    Your tuner can tell you easily if it is compressor surge. Would save you a bunch of time. What does he say?

    Mike W

  6. #6
    Still haven't been to the tuner since he's 65 miles away. Our landlord says we're getting evicted if I pop the hood in the garage ever again, so I suppose I'm gonna surrender soon.

    Problem comes and goes. One minute the car dies and I'm thinking "oh I'm screwed, better call a tow truck" the next minute I restart the car, totally fine for a week or two straight. Also when it does die it smells weird, either rich or oily or something. Plugs 1, 2, and 4 got oil on them too.

    Here are my wack ass, totally unscientific troubleshooting efforts so far:

    Sodomized the PCV valve every which way.
    Fiddled with the previous owner's subwoofer trunk wiring.

    It's not science, but I could swear doing the above makes the problem go away. I'll update this thread if I have a proper solution. One thing I notice is that every time I throw stuff in the trunk the problem either appears or disappears. Maybe the wires are shorting on something. I'm going to pull all that crap out this week, get a new battery and clean connectors.

  7. #7
    Canyon Racer evo_jfa's Avatar
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    I think it could help is you share your location. Maybe guys here can give you another tuner or shop that can help you

  8. #8
    I'm in West LA, the tuner is far East. He's inviting me to stop by but I'm just being stubborn. I'm afraid it's something simple and I'll waste 130 miles round trip on being a doofus. Got a new PCV valve tonight. I could swear the throttle response has improved, need to verify.

    My previous car was tuned by RRE so I'll probably be coming back for a 2.3 once I screw this up. Pick a card Mike, any card. Unfathomable debt is the American way of life, I'm ready.

  9. #9
    Canyon Racer evo_jfa's Avatar
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    If you are west LA, there is not too much distance. I think the best to do is take your time and plan a route off highways. Other is ask for a favor in West LA for data logging and work in a e-tune fashion. You can send the file to the tuner or even post the data here or Evom. I'm sure you someone can help you for a beer and a burger.

  10. #10
    Not at Evos have the same reading at idle, or decel on the boost gauge. You might want to take a look at the vacuum hose from the FPR line to boost sensor and check for cracks at the ends. If your boost reading ever changes from what they usually are, that's the first place I'd look!
    You may want to pull your IAC, and see if it looks stripped on the bottom . Good luck!

    N.

  11. #11
    Not So Newbie
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    Evo IX, 91 eclipse gsx, and other commuters...
    Do you know where the remote wire is hooked up to (for the amp)? There is a possibility that he may have tapped into wrong place in the wiring harness or even to fuel pump. I have seen weird things like this. I once saw a newer corolla that was diagnosed with a bad ecu but after installing a new ECU it was still acting up at times. We ending up finding out the wiring harness in the trunk was getting pinch whenever there were things in the trunk. We repaired the wiring and put extra padding around the wires where it was getting pinched. It was having the same type of idle shutter...

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