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2G Trying to fix this idle issue

Posted by Talon Cooke, Feb 15, 2020

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  1. Talon Cooke

    Talon Cooke Proven Member

    32
    4
    Joined Jan 27, 2020
    Winnipeg, MB, Canada
    Hey guys ive been trying to fix this idle issue. My car has been idling funny since ive gotten it. I took out the iac valve, cleaned it and it sort of fixed it for a little while although it still idled high. Now its back to how it was but even a bit worse. The idle is not consistent at all and sometimes jumps up to 2500 then brings itself back down. Its always after i come to a stop at a red light or stop sign and put it into neutral it will jump around for a bit all willy nilly then stabilize at 1500 or 2000. I posted a video so you guys could see what im talking about. Any help is very much appreciated
     

    173  1

    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  2. motomattx

    motomattx Proven Member

    2,203
    850
    Joined Dec 9, 2010
    wampum, Pennsylvania
    What mods are on the car? are the coolant lines still running to the throttle body?
     

    Drag Race Build 3K  24

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  3. Talon Cooke

    Talon Cooke Proven Member

    32
    4
    Joined Jan 27, 2020
    Winnipeg, MB, Canada
    if you mean the 3 prong connectors on the top then no. they have been removed and blocked off. Curious why someone would do this?
     

    173  1

    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  4. motomattx

    motomattx Proven Member

    2,203
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    Joined Dec 9, 2010
    wampum, Pennsylvania
    I am talking about the two small 3/8 inch coolant hoses at the bottom half of the throttle body, are those still connected?
     

    Drag Race Build 3K  24

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  5. Talon Cooke

    Talon Cooke Proven Member

    32
    4
    Joined Jan 27, 2020
    Winnipeg, MB, Canada
    yes they appear to be both still connected. however as i stated above the other lines running to the top of the TB have been removed
     

    173  1

    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  6. motomattx

    motomattx Proven Member

    2,203
    850
    Joined Dec 9, 2010
    wampum, Pennsylvania
    Those were emissions lines that sometimes get removed to clean up the engine bay. Have you set your biss screw? whats a biss screw you ask? how would I set it you ask?

    https://www.dsmtuners.com/threads/biss-screw-adjustment.425941/
     

    Drag Race Build 3K  24

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  7. Talon Cooke

    Talon Cooke Proven Member

    32
    4
    Joined Jan 27, 2020
    Winnipeg, MB, Canada
    touching that thing is what led me to create my original "I broke my car" post LOLol. i tried adjusting it before to fix this problem and for some reason it completely ruined it and i could not get it to run at all after. after adjusting it i got the idle down but then it would just stall out on me after revving it. Then it got to the point where it wouldn't even run any more and i had to take it in. I dont think this is the problem tho because of how erratic and inconsistent the idle is. It jumps around and after i give it a throttle blip it will fall down and nearly stall out but then jump back up.
     

    173  1

    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  8. Michael Helsel

    Michael Helsel Probationary Member

    25
    6
    Joined Dec 26, 2015
    Youngsville, North Carolina
    Have you boost leak tested it? Does the throttle hit the throttle stop on the back of the throttle body? Make sure all of the barbs and fittings on the intake manifold and throttle body are connected to something or capped. A boost leak test would also tell you, but you can spray some brake cleaner or starter fluid around the throttle body gasket and intake manifold gasket to seti if they're allowing air past. You also want to make sure the oring for your iac is in good shape.
     

    Street Build 787  1

    1997 Mitsubishi Eclipse Spyder GST
    awd · manual · 2G DSM
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    Talon Cooke likes this.
  9. motomattx

    motomattx Proven Member

    2,203
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    wampum, Pennsylvania
    You might actually have a failing fiav assembly if nothing else checks out as wrong, you could try blocking it off.
     

    Drag Race Build 3K  24

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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    Talon Cooke likes this.
  10. jcastello214

    jcastello214 Proven Member

    82
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    Joined Jul 17, 2012
    Daly City, California
    To troubleshoot this, a boost leak test is required to make sure you have no external leaks. High idle or idle surge is caused by too much air going past the throttle plate or air getting in after the throttle plate that’s not metered. Here’s a list:

    1) throttle cable not adjusted correctly
    2) IAC stuck open
    3) throttle shaft seals leaking
    4) BISS not adjusted properly
    5) FIAV stuck open after warm up
    6) throttle plate not closing all the way
    7) TPS Sensor Not adjusted correctly
    8) intake gasket leaking
    9) fuel injector O-Rings not sealing in the intake
    10) throttle body gasket leaking

    most common with dsms is the FIAV and it’s hard to test. Rule everything out and if it’s the FIAV, pop the freeze plug out on the throttle body and turn the plate all the way in to bypass it or use a block off plate. Done.

    hope that helps!
     

    Street Build 684  0

    1994 Eagle Talon TSi AWD
    automatic · 1G DSM
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    Talon Cooke likes this.
  11. motomattx

    motomattx Proven Member

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    wampum, Pennsylvania
    There is a very easy free way to test the fiav being the problem, unplug the mass air sensor assy, pull the intake from the throttle body, start the car (yes the car will run like this and can even be driven like this if you needed to, I have) and as its idling cover the fiav air bypass port in the throttle body with a finger, if the idle settles down, there is a problem in that area, the same can be done with the other port for checking the isc control of the idle.
     

    Drag Race Build 3K  24

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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    Talon Cooke likes this.
  12. Talon Cooke

    Talon Cooke Proven Member

    32
    4
    Joined Jan 27, 2020
    Winnipeg, MB, Canada
    update: haven't done much testing since this post aside from spraying carb cleaner around the throttle body/ intake manifold; Nothing happened. but, i recently noticed a small leak in the welds on my exhaust manifold. So i am wondering if you guys think that this could be the issue. I will be doing the fiav test that motomatt mentioned above in the mean time. Thanks!
     

    173  1

    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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