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General Extremely High Idle

Posted by Z3r0to1, May 22, 2018

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  1. Z3r0to1

    Z3r0to1 Proven Member

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    Markle, Indiana
    So I just got the car running, and for whatever reason the car is idling at 4500rpm. I have tried adjusting the BISS screw and attempted to reset the ISC (although I'm going to try it again). Does anyone know of any other thing that could be causing an idle that high?
     

    216  0

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  2. pauleyman

    pauleyman DSM Wiseman

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    Throttle cable or throttle plate itself. Reach over and push on the throttle lever and make sure its closed.
     

    Street Build 2K  1

    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  3. Z3r0to1

    Z3r0to1 Proven Member

    36
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    Joined Mar 21, 2018
    Markle, Indiana
    That'll be the first thing I check in the morning. Thanks so much!
     

    216  0

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  4. Z3r0to1

    Z3r0to1 Proven Member

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    Markle, Indiana
    Update: So I went through and completely disconnected the throttle cable to be sure it wasnt that, and the problem is still occuring. I also checked the throttle plate and it is shut. Could it be a computer issue or is it something mechanical? Also, would I benefit from a boost leak test?
     

    216  0

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  5. pauleyman

    pauleyman DSM Wiseman

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    You've got a big leak most likely. Air has to get into the motor from somewhere
     

    Street Build 2K  1

    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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    steve likes this.
  6. chrysler kid

    chrysler kid Proven Member

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    Mckinney, Texas
    Boost leak test will show you where any vacuum or boost leaks are.

    You likely have a bad air leak into the intake causing a high idle
     

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    1998 Mitsubishi Eclipse GST
    fwd · automatic · 2G DSM

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    1996 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM

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    1996 Mitsubishi Eclipse GST
    14.1 @ 97 · 2G DSM
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  7. Z3r0to1

    Z3r0to1 Proven Member

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    Joined Mar 21, 2018
    Markle, Indiana
    So I went through and did leak tests multiple times to fix whatever areas were leaking. After fixing them, the idle is still jumping straight to 4000ish rpm, but I tried running it without the ISC connected, and this caused it to behave completely different. It not only was around where the idle needed to be, but it started up easier too. The only issue was that it was only capable of holding a low rpm for a few seconds maximum before it sputtered and died. Any ideas? Any thoughts are appreciated
     

    216  0

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  8. pauleyman

    pauleyman DSM Wiseman

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    oklahoma city, Oklahoma
    Test the isc and check the circuit.
     

    Street Build 2K  1

    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  9. Z3r0to1

    Z3r0to1 Proven Member

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    Markle, Indiana
    Ill be sure to, but if the engine is struggling when the ISC is unplugged and the BISS screw allowing for as much air as possible to get by, then could the issue be something else?
     

    216  0

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  10. iceguru1114

    iceguru1114 Proven Member

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    Atlanta, Georgia
    I found this, maybe it will help you out:
    https://www.dsmtuners.com/threads/dsm-isc-motor-testing-replacement.386663/

    If the ISC is not the issue, the symptom basically sounds like too much air is making it into the cylinders at idle. Think about everything that could possibly allow air to enter the intake side of the engine and start checking things off the list (hint: this includes the breather system).

    Best of luck.
     

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    1992 Mitsubishi Galant VR-4
    awd · manual · Galant VR-4
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  11. Vegas smith

    Vegas smith Proven Member

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    Isc issues usually don't lead to a 4k idle. You're looking at a huge leak.
     

    Street Build 2K  10

    1993 Eagle Talon TSi AWD
    awd · manual · 1G DSM
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  12. Z3r0to1

    Z3r0to1 Proven Member

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    Markle, Indiana
    When I boost leak tested it the only leak was at the throttle body gasket, but I've since fixed that. I tested afterward and there were no leaks anywhere. Is there something I'm missing?
     

    216  0

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  13. Z3r0to1

    Z3r0to1 Proven Member

    36
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    Joined Mar 21, 2018
    Markle, Indiana
    So I went out and I started attempting to adjust the BISS and mess with the throttle cable while it was revved so high, and I found that once I got it running I could bring it back down by turning the throttle cable back to where I thought it should be at idle. After checking the throttle cable, its neither a cruise control or non cruise control (previous owner must've hacked it). Does that sound like a side affect of a stuck throttle body?
     

    216  0

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  14. Vegas smith

    Vegas smith Proven Member

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    I'm not sure what you mean.
     

    Street Build 2K  10

    1993 Eagle Talon TSi AWD
    awd · manual · 1G DSM
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  15. Z3r0to1

    Z3r0to1 Proven Member

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    Joined Mar 21, 2018
    Markle, Indiana
    Okay so I went to start it again, and the idle jumped to 4k like it did before. After that I cranked the BISS screw down until it adjusted it lower, but I would estimate that the idle was probably at 2.5/3k. After that I turned the throttle body by hand to see if it was stuck open. This brought the idle down significantly, and into an area that I would be comfortable with. After this though I noticed that the throttle cable wasn't the correct length for the non cruise control state of the car. I was just wondering of this could've been the issue all along, and if so why the car stuttered out and died shortly after I left it alone to idle at the spot I had gotten it to
     

    216  0

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  16. Vegas smith

    Vegas smith Proven Member

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    Houston, Texas
    It sounds like you have either have the wrong throttle cable or it isn't adjusted properly. Once you fixed that, you probably have your biss screw turned in all the way and that will cause the car to die. Make sure throttle situation is perfect then search how to adjust BISS screw.
     

    Street Build 2K  10

    1993 Eagle Talon TSi AWD
    awd · manual · 1G DSM
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  17. Z3r0to1

    Z3r0to1 Proven Member

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    Joined Mar 21, 2018
    Markle, Indiana
    Is there anyway to make the spring on the throttle body "springier"? (r.i.p. english)
     

    216  0

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  18. Vegas smith

    Vegas smith Proven Member

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    There should be two springs on the throttlebody. Perhaps it was taken apart and not put together properly. Maybe they only put one spring back on.
     

    Street Build 2K  10

    1993 Eagle Talon TSi AWD
    awd · manual · 1G DSM
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  19. Z3r0to1

    Z3r0to1 Proven Member

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    Markle, Indiana
    Where are they located at? I was talking about the main one on the outside that is on the assembly that the throttle cable connects to. It felt a little weak when I turned it
     

    216  0

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  20. Vegas smith

    Vegas smith Proven Member

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    Those are the springs I'm referring to. It looks like 1 but it's actually 2 springs.
     

    Street Build 2K  10

    1993 Eagle Talon TSi AWD
    awd · manual · 1G DSM
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  21. Z3r0to1

    Z3r0to1 Proven Member

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    Joined Mar 21, 2018
    Markle, Indiana
    Oh okay, didnt notice that before LOL
     

    216  0

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  22. brian9397gsx

    brian9397gsx Proven Member

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    sioux city, Iowa
    I've just had the same issue I've been working on for a buddy on his 1g. There were so many issues. I found out his buddy rebuilt his Tb and put the throttle blade in upside down and backwards. He ported it where the plate rides so it wouldn't seal. Then after I got another tb in and rebuilt it damn thing acted the same. Mind you I already fixed every damn boost leak on this piece of garbage. I finally pulled the iac out again and compared it to another one and found the end wasn't right kinda deformed with a whole area around the outside missing. I replaced it now it is probably the best idling dsm i've seen in a long time.
     
    brian9397gsx

    2K  0

    1993 Mitsubishi Eclipse GSX
    19.80 @ 35.55 · 1G DSM
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  23. Z3r0to1

    Z3r0to1 Proven Member

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    Joined Mar 21, 2018
    Markle, Indiana
    I went through and searched for how to clean and dissassemble the throttle body, but I'm pretty sure that it wasn't put back together correctly last time. I can only put one spring under tension as of now. If anyone has a picture of what it should look like when assembled correctly, like the placement of the hooks on the springs it would be extremely appreciated
    EDIT:
    Also, I started the car up with a brand new alternator belt that started smoking after I had just gotten out of the front seat from turning it over. Goven the car was still jumping to that idle of 4k, but I didn't think that would be any reason for the belt to start smoking. It was extremely hot to the touch, almost as hot as the exhaust mani, and was squeaking. I hate to pile onto the thread with a completely unrelated question, but I don't know if this was due to my tightening of the belt, or if the alternator had gone bad...
     
    Last edited: Jun 17, 2018

    216  0

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  24. tk106

    tk106 Proven Member

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    Here's a good video on rebuilding 2g tb.



    If you've had the tps off, I'd remove it to make sure the two prongs are seated correctly on the tps.

    As far as the belt smoking, remove the belt and make sure you can turn all the pulleys by hand and none are binding. The way I check belt tension is to twist the belt 90 degrees once it's on.
     

    Street Build 1K  8

    1992 Eagle Talon TSi AWD
    awd · manual · 1G DSM
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  25. Vegas smith

    Vegas smith Proven Member

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    Houston, Texas

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    1993 Eagle Talon TSi AWD
    awd · manual · 1G DSM
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