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Thread: Overboost protection troubles

  1. #1
    Garrett booster
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    Overboost protection troubles

    I am in need of some advice, i have an 85 omni converted to 87 electronics. And the car rev to 3500 rpm and dies. I have replaced

    - fuel pump with fuel rail pressure of 50 psi
    - map sensor with from 87 car
    - LM brand new from dodge dealer.

    Also checked timing, looks good. Checked map sensor solenoid pull vacuum on black nipple under map sensor connection and hit with 12v and vacuum drops.

    I am have also tried to disconnect wastegate actuator from swingvalve and same things. I also only have codes 12 and 33 in LM.


    I am lost for ideas at this point, any help would be great.

  2. #2
    Hybrid booster
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    Re: Overboost protection troubles

    Define dies?

    You put 12 volts on map sensor?
    Let us know.

  3. #3
    turbo addict Tony Hanna's Avatar
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    Re: Overboost protection troubles

    Quote Originally Posted by rosie View Post
    You put 12 volts on map sensor?
    If I'm reading correctly, he put 12v to the baro read solenoid.

  4. #4
    turbo addict
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    Re: Overboost protection troubles

    sounds like timing to me. 3k or 2k limits would be a sensor throwing a code. Tripple Check your cam timing.

  5. #5
    Garrett booster
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    Re: Overboost protection troubles

    i put 12v to the solenoid under map sensor
    and i will triple check timing thank you.

  6. #6
    Hybrid booster
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    Re: Overboost protection troubles

    Yea, but what did you mean by die's at 3500? Shuts off like you hit a wall of overboost goodness? Bogs out? Car turns off?

    Could be a clogged cat, loose wire, bad cal.... diag all over the place. Need some more info to focus your diag or you'll just be shotgunning componants/wires.

  7. #7

    Re: Overboost protection troubles

    The only reasons why the motor cuts out around ~4000RPM?

    Cam timing off
    map sensor problem
    Overboost cutout

    The best way to rule cam timing? Can you rev to redline in neutral? If you can't rev past 4000RPM at idle, cam timing.

    A failing map sensor won't always throw a code. It will operate in spec for the ECU, but will give faulty readings. Check your vacuum line and test sensor.

    Overboost cutout usually happens around 4000RPM on a near stock car. Its pretty much the point the car will make full boost.

    I haven't seen a cat cause a cutout. I've seen it limit boost past 4000RPM. My car broke up, causing my boost to flutter above 4000rpms.

    Quote Originally Posted by GLHNSLHT2 View Post
    sounds like timing to me. 3k or 2k limits would be a sensor throwing a code. Tripple Check your cam timing.
    James Dempsey Jr 91 Dodge Shadow ES convertible 95 Dodge Neon Sport sedan 2.4 5spd

  8. #8

    Re: Overboost protection troubles

    What codes are being posted??

  9. #9
    Buy my stuff!!!!!!!!!!! :O) Turbo Mopar Vendor turbovanmanČ's Avatar
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    Re: Overboost protection troubles

    Could be a bad TPS, they do that when they go bad.
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  10. #10
    Hybrid booster
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    Re: Overboost protection troubles

    Come on you guys, lets get some acurate symptoms before we swap out every part on his car! So far it dies.... Dies? What kind of dies? How far did the conversion go, just the map sensor? Full T2? Anyone knows from previous posts and not telling ?

    Could be anything from intake to exhaust. More detailed info please Ikknown.

  11. #11
    Garrett booster
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    Re: Overboost protection troubles

    ok i got the dodge tech at work to have a lookey at the car and found a fuseable link in the drivers side burnt it was the orange one going to two red power wires. Temporary fix the fuseable link and the car revs to redline in neutral and acts normally now but still hit and miss. Like theres and wire shorting some where but just need to find the short. Any ideas my service manuals are for an 88 and i dont have smec.

    Thank you.

  12. #12
    Hybrid booster
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    Re: Overboost protection troubles

    Hit and miss what?

  13. #13
    Garrett booster
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    Re: Overboost protection troubles

    the car goes in and out of what feels like overboost protection
    it looks like the fuseable link go to the power module and igniton switch

  14. #14
    Hybrid booster
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    Re: Overboost protection troubles

    So it bucks at those RPM's right? That's usually the MAP sensor or the baro. Do you have the schematics? Wring out the wires so you know they're going to the right place. That's assuming your vacuum lines are all in the right spot and your map is getting a good vacuum source.

  15. #15
    Garrett booster
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    Re: Overboost protection troubles

    Ok, the car is getting better. If i have the car idling and then wot the engine revs to 3500 rpms and then falls back down to idle and keeps going until i let off wot. But if i get on the gas slowly it will rev to redline and build boost once driven. I think i have a shorted wire it ethier the red or pink wire coming off the orange fuseable link. My wiring diagrams so me the power module and ignition switch but very vague.

  16. #16
    turbo addict Tony Hanna's Avatar
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    Re: Overboost protection troubles

    That really sounds like the limp-in limiter you'd get from a bad map sensor. Though it should have set a code for it and turned the check engine light on. Unless maybe you missed a blink when you were reading the codes and that code 12 is actually a code 13 (map sensor pneumatic failure). That would explain a lot. Otherwise, I dunno...

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