High idle when warm after driving

Posted by TurboMR2, Apr 23, 2010
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  1. TurboMR2

    TurboMR2 Proven Member

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    Gainesville, Florida
    ive searched and searched and cant find anything with the same problem i am having. this just started last night. after the car warms up and i drive it for a few min the car will idle high when i stop around 2k rpms. if i hit the gas and give it a little rev it drops down to 1500 rpms. every once in awhile it will drop down to 1100 rpms. its a 95 gst 6 bolt bottom end dsm link greddy ic and bov 650cc injectors 255 fuel pump new spark plug and wires replaced a week ago. even adjust the biss screw doesnt change. it can adjust it to where is want it to idle put as soon as the rpms go about 2k it stops a 2k or 1500k. need some help, working on the car now.
    #1
  2. juzslidin

    juzslidin Proven Member

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    butler, New_Jersey
    did u check for a vac / boost leak after the throttle body ? also make sure the throttle is closing all the way
    #2
  3. haswesley

    haswesley Proven Member

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    Colorado Spring, Colorado
    Sounds like your idle air controller went bad or is malfunctioning for some reason. The idle air control allows additional air into the intake which in turn raises idle.
    #3
  4. TurboMR2

    TurboMR2 Proven Member

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    Gainesville, Florida
    ok so after driving it all day today with the high idle i let it sit for alittle while and cool down. now its not doing it. i drove it for alittle and then it started to idle at 1500 rpms but only after driving it for alittle while. so then i adjusted the tps properly and its not doing it but i didnt drive it for very long.
    #4
  5. turboawd420

    turboawd420 Proven Member

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    palatine, Illinois
    try and loosen your throttle cable a little and see if the rpm drop thats what mine was doin.
    #5
  6. da1sexmonk83

    da1sexmonk83 Proven Member

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    Paducah, Kentucky
    TurboMR2 did you ever fix this? If so what was the problem? Mine just started doing this today.


    ECU+
    AEM Fuel Pressure Regulator 43.5psi
    6 bolt motor swap
    Balance Shaft Eliminator Kit
    ARP head and block Bolts
    Bored .20 over
    Head milled 50 thousandths over
    Ralliart MLS head Gasket
    JE Pistons 8.7:1
    Ported Intake Manifold
    IACV block off plate
    Specte high flow intake filter
    Injen intake tube
    Front mount Intercooler
    Pacesetter header
    3 Inch Exhaust
    Bullseye 50 Trim Turbo TO4B
    Crushed 1g BOV recirculated
    Walbro 255 HIGH PRESSURE fuel pump
    FIC 750 cc Injectors
    Innovate LC-1 Wideband o2 sensor simulating front O2
    Alternator uprade from to 90 amp spyder
    #6
  7. rarest_90_DsM

    rarest_90_DsM Proven Member

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    akron, Ohio
    Did you ever get this problem fixed I am having the same issue?????
    #7
  8. sik4g63

    sik4g63 Proven Member

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    b town, West_Virginia
    Check your ISC and check for boost or vacuum leaks. Or the TPS. Another thing could be that the TB is dirty and could be getting stuck open a little bit. Also like stated above, you could try loosening your throttle cable to see if that is the problem. I had a bad idle surge problem for a while and when my water pump went out, I got it replaced the surge went away. Now when I start my car it idles at 3k until engine is warm. I have narrowed it down to the TPS or the ISC. Hope this helps.
    #8
  9. 321

    321 Proven Member

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    Richmond, Virginia
    I am not sure if the 2gs have a idle switch or not. If they do, check it. I had a similar problem on my 1g and the idle switch had gone bad. If you have any way of veiwing live data, then check your tps reading and idle state.
    #9
  10. slikvik

    slikvik Proven Member

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    Prosser, Washington
    I had the same problem for the longest time on my 92 laser turbo. I finally got a rebuilt throttle body with the fiav bypass plate and my problem went away.
    Last edited: Sep 1, 2010
    #10
  11. Shnizzle

    Shnizzle Proven Member

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    Las Vegas, Nevada
    This happened to me almost exact same problem except it was holding 2k rpms but I loosened the throttle cable just a touch and totally fixed the problem.
    #11
  12. mr2krazee

    mr2krazee Proven Member

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    spokane, Washington
    maybe check the voltage from your TPS and verify that it is in spec. i know that when my TPS was adjusted out of spec i had a high idle that i could occasionally get to go lower. also could be the throttle cable starting to get worn out.
    #12
  13. arabeclipse

    arabeclipse Proven Member

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    detroit, Michigan
    I'm having the same issue. After 20 mins of city driving, it goes to 1500 to 2000 rpms and stays there. I loosened up the cable and it still does it. But if i drive on the highway for 15 minutes, then it's as if nothing happened. No boost leaks and my TPS reads .62 which is as close as I can get it by hand. Maybe my ISC?
    #13
  14. williamdsm

    williamdsm Proven Member

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    Newfield, New_Jersey
    Yes it definitely could be. Pull it out and see what kind of reading you get on it with a multimeter. Should read between 28-32 ohms I think. Check out this video by Jafro. Mines bad and I have high idle issues as well. My new one should be here tomorrow.

    [ame=http://www.youtube.com/watch?v=KibYz21IMA0]DSM ISC motor testing & Replacement - YouTube[/ame]
    #14
  15. Afizzle

    Afizzle Proven Member

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    Dallas, Texas
    #15
  16. SeaveeDSM

    SeaveeDSM Proven Member

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    Miami, Florida
    Do a boost leak test and listen for leaks at throttle body (TB) shaft seals and/or TB gaskets

    If the seals are bad you can replace them yourself - search for how to threads - a bit of a PITA or as an alternative send the TB out for rebuild. I sent mine recently to Steve Monroe at Throttlebodys.com Great service and very reasonable price. The TB gaskets are easy to replace but still also require removal of the TB to get at.
    Last edited: May 5, 2013
    #16
  17. arabeclipse

    arabeclipse Proven Member

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    detroit, Michigan
    Just checked it. 5&6 is shot on mine too. Guess that was the culprit. Thanks man.
    #17
  18. Boost_Junkie301

    Boost_Junkie301 Probationary Member

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    leonardtown, Maryland
    Check IAC, then do a smoke test and look for leaks. Its a waiting game, but well worth it to find the vacuum leak.
    #18

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