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1G Idle Surge (up & down)

Posted by Blkapache01, Dec 11, 2018

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  1. Blkapache01

    Blkapache01 Proven Member

    34
    3
    Joined Mar 28, 2017
    Birmingham, Alabama
    Hey folks,

    I need some help. My Talon is reving up and down on the idle and I saw that whenever I hit the sensor on top of the throttle body the speed changes. I included a pic of the sensor in case someone can tell me what it's called.

    It's a 2.0 non turbo.
    I wanted to include the video but the file is too large.

    BTW, I already replaced the mass air flow sensor, new TPS sensor, cleaned throttle body, got a new Idle Air Control Valve and cleaned the EGR valve.
     

    Attached Files:

    Last edited by a moderator: Dec 12, 2018

    Street Build 507  0

    1991 Eagle Talon N/T
    manual · 1G DSM
    Loading...
  2. motomattx

    motomattx Proven Member

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    637
    Joined Dec 9, 2010
    wampum, Pennsylvania
    Have you tried plugging that closed throttle sensor back in?, try that first and do you have any vacuum leaks? have you checked?
     

    Drag Race Build 3K  23

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  3. Blkapache01

    Blkapache01 Proven Member

    34
    3
    Joined Mar 28, 2017
    Birmingham, Alabama
    Hey, yeah, I only left it off to take a clear pic of it. I plugged it back right after I took the photo. I didn't find any leaks. Someone said in another thread that some of these have purge canisters that can leak but I don't know if mine has one. Supposed to be under the passenger side of firewall but I didn't see one.
     

    Street Build 507  0

    1991 Eagle Talon N/T
    manual · 1G DSM
    Loading...
  4. drcolt

    drcolt Proven Member

    56
    11
    Joined Jun 27, 2003
    Toronto, ON, Canada
    How long have you owned the car? What is the history with the car in regards to recent work done.
    Did it used to idle welll?
    Check injectors seals, Throttle body shaft seals and biss screw and seal.
    Has TB been installed correctly? Meaning throttle plate adjustment, tps adjustment and TPS closed switch. Has all that been set according to factory spec?
    Did you have a chance to inspect the FIAV in the TB?
     

    Street Build 853  6

    1989 dodge colt gt
    fwd · manual · 4G63t Swapped

    Street Build 877  2

    1988 dodge colt 100 lx sedan turbo
    299 whp · 286 lb/ft · 4G63t Swapped
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  5. motomattx

    motomattx Proven Member

    1,875
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    Joined Dec 9, 2010
    wampum, Pennsylvania
    Im assuming that you still have the coolant lines going to the throttle body?
     

    Drag Race Build 3K  23

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  6. Vegas smith

    Vegas smith Proven Member

    2,757
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    Joined Dec 2, 2002
    Houston, Texas
    The part you reference in the pic is actually the idle position switch. It needs to be adjusted correctly (search) for the car to idle correctly. The idle issue you have is idle surge and is well documented. It's usually a vacuum leak or a BISS screw out of adjustment.
     

    Street Build 3K  10

    1993 Eagle Talon TSi AWD
    awd · manual · 1G DSM
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  7. Blkapache01

    Blkapache01 Proven Member

    34
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    Joined Mar 28, 2017
    Birmingham, Alabama
    Yes, indeed.

    Well, I've owned it for 25 years, TBH.

    I had it sitting up the past 7 years in my garage when the clutch went out and ignored it. Last year, I decided to resurrect it. New clutch, new starter, new timing belt, water pump, engine coolant flush, new head gasket, new piston rings, new idle air control valve, new spark plugs/plug wires, new thermo emissions control valve, fuel injector cleaned and new o-rings, BISS screw o-ring, TPS sensor, Mass Air Flow Sensor, new exhaust manifold, throttle body gasket and cleaned and torqued parts to spec.

    Even when it was my daily driver, the idle up and down happened after the first few years I owned it but replacing the IACV worked for a while but came back later.

    Now that it's been sitting up, I just wonder what else could be causing it.

    You know, for years I never knew what that part was called. Couldn't find it in my service manual. Have you had to do an adjustment?
     
    Last edited by a moderator: Jan 4, 2019

    Street Build 507  0

    1991 Eagle Talon N/T
    manual · 1G DSM
    Loading...
  8. Vegas smith

    Vegas smith Proven Member

    2,757
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    Joined Dec 2, 2002
    Houston, Texas
    Any time you are having idle issues you need to check the that switch, the biss screw and for air leaks all throughout the system.
     

    Street Build 3K  10

    1993 Eagle Talon TSi AWD
    awd · manual · 1G DSM
    Loading...
  9. Blkapache01

    Blkapache01 Proven Member

    34
    3
    Joined Mar 28, 2017
    Birmingham, Alabama
    Thanks, Vegas. Does that switch ever go bad or do they just require adjusting?
     

    Street Build 507  0

    1991 Eagle Talon N/T
    manual · 1G DSM
    Loading...
  10. Vegas smith

    Vegas smith Proven Member

    2,757
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    Joined Dec 2, 2002
    Houston, Texas
    I've never heard of one going bad.
     

    Street Build 3K  10

    1993 Eagle Talon TSi AWD
    awd · manual · 1G DSM
    Loading...
  11. 1990TSIAWDTALON

    1990TSIAWDTALON Moderator

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    Independence, Kansas
    And make sure that the throttle body is GROUNDED so that the switch works correctly. It just tells the ECU that the throttle is completely closed, but needs to throw that circuit to ground for it to work. That is what the little metal strap is for on some TB's, to ground it so when the idle switch is closed, it grounds. :)
    I have added a ground to mine to make sure it operates correctly.
     

    Street Build 3K  27

    1992 Eagle Talon TSi AWD
    awd · automatic · 1G DSM

    522  14

    1990 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM

    444  18

    1967 Chevrolet Camaro RS
    rwd · automatic · Misc Vehicles

    Street Build 642  4

    1998 Eagle Talon TSi
    fwd · manual · 2G DSM

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    1990 Eagle Talon TSi AWD
    13.620 @ 108.460 · 1G DSM
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  12. Blkapache01

    Blkapache01 Proven Member

    34
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    Joined Mar 28, 2017
    Birmingham, Alabama
    Thank you. I'll give that a go.
     

    Street Build 507  0

    1991 Eagle Talon N/T
    manual · 1G DSM
    Loading...
  13. motomattx

    motomattx Proven Member

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    wampum, Pennsylvania
    The fast idle air valve (fiav) does go bad here and there, if all else checks out I would look for another.
     

    Drag Race Build 3K  23

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    Loading...
  14. drcolt

    drcolt Proven Member

    56
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    Joined Jun 27, 2003
    Toronto, ON, Canada
    Take a look at your engine temp sensor and connectors. Like an another member mentioned, ensure the coolant lines are still connected to the throttle body.
    Has the ECU ever been inspected?
     

    Street Build 853  6

    1989 dodge colt gt
    fwd · manual · 4G63t Swapped

    Street Build 877  2

    1988 dodge colt 100 lx sedan turbo
    299 whp · 286 lb/ft · 4G63t Swapped
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  15. Blkapache01

    Blkapache01 Proven Member

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    Joined Mar 28, 2017
    Birmingham, Alabama
    I replaced the ECU with a junkyard part. I made sure the model/ECU numbers matched. There wasn't any change in the performance, though.
     

    Street Build 507  0

    1991 Eagle Talon N/T
    manual · 1G DSM
    Loading...
  16. Auto RS T

    Auto RS T Proven Member

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    Norwalk, Ohio
    Any cracks in the air intake tube?
     

    Street Build 873  4

    1992 Plymouth Laser RS Turbo
    10.952 @ 125.27 · 1G DSM

    746  17

    1990 Eagle Talon TSi AWD
    12.104 @ 118.450 · 1G DSM
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  17. steve

    steve DSM Wiseman

    12,760
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    Joined Feb 3, 2002
    St. Charles, Illinois
    Idle surging is caused by the engine wanting to idle higher than the coasting idle speed and when the ECU sees that the throttle is closed (via the IPS being grounded) and that the engine RPMs are higher than the programmed RPM's it turns the injectors off until the RPMs drop and then back on to keep the engine from stalling.

    The usual cause is idle air bypassing the closed throttle from leaks and misadjustments. Everything that connects to the intake manifold is suspect and given all the things you've touched a general pressure test from the throttle body might be useful to identify sources. Once your sure there are no leaks setting the basic ignition timing and BISS adjustment come next.

    On a 1G the IPS also acts as the throttle stop. It limits how far closed the butterfly will go to keep keep blade from jamming in the bore and sets how much air can bleed past. Along with the BISS, FIAV, and ISC control the idle air. The factory service manual cautions against adjusting the IPS normally since it's a critical piece for the TB to work correctly. It then goes on to specify something like 15/16's of a turn after the IPS plunger contacts the throttle pulley.

    For those who suggested checking that the IPS was grounding, I'll remind you that the ECU won't attempt decel fuel cut if the IPS doesn't ground the signal when the throttle is closed. So having idle surge is a good indicator that the IPS is working, just pull the wire and see.

    The ECU won't attempt to manage the idle speed at all if the IPS isn't telling the ECU that the throttle is closed. That means you also won't see the ECU attempt to raise the idle speed when the Power Steering pump is active, the alternator is creating load, or the AC is on.

    Both of your ECUs should be inspected for capacitor leakage and that the ISC drivers are not damaged. Every 1G ECU is plagued by the capacitors leaking over time and must be replaced and any leakage corrected.
     

    3K  0

    1991 Mitsubishi Eclipse GSX
    manual · 1G DSM
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    19Eclipse90 likes this.
  18. Blkapache01

    Blkapache01 Proven Member

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    Joined Mar 28, 2017
    Birmingham, Alabama
    None that I could see or feel. I heard a hiss but it wasn't coming from the air intake tube. Been difficult to track that "phantom" hiss.

    I sold the other ECU on eBay a couple of years ago because it was malfunctioning. Meaning, the CEL wouldn't even light up when key was in the ACC position so I knew it had to be ECU related. I got the same type with same matching model number as my old one from a junkyard and instantly, the CEL was working again, just had the same issue of improper idling. I thought that I read on here that someone used to fix ECUs on this site. Is that still the case and if so, how much to send it off for repair?

    Replaced it with a black/tan part online. No change.

    How did you ground yours? From what I could tell, with it bolted and the negative wires bolted to the intake, I thought it already was.
     
    Last edited by a moderator: Nov 24, 2019

    Street Build 507  0

    1991 Eagle Talon N/T
    manual · 1G DSM
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  19. 1990TSIAWDTALON

    1990TSIAWDTALON Moderator

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    There is usually a ground strap that goes thru one of the TB bolts and has a screw on top of the TB that it grounds to. Sometimes those have been tore up and are missing. I just ran a ground to that screw so that the complete TB was grounded for sure.
     

    Street Build 3K  27

    1992 Eagle Talon TSi AWD
    awd · automatic · 1G DSM

    522  14

    1990 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM

    444  18

    1967 Chevrolet Camaro RS
    rwd · automatic · Misc Vehicles

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    1998 Eagle Talon TSi
    fwd · manual · 2G DSM

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    1990 Eagle Talon TSi AWD
    13.620 @ 108.460 · 1G DSM
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  20. steve

    steve DSM Wiseman

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    St. Charles, Illinois
    I'm sure there are several people on this site that fix ECU's on the side but since I shut down my ECU business 8+ years ago I only recommend using the guys at ECMTuning due to their knowledge, pricing, and after the sale support. They know what to look for and how to correctly fix what they find.
     

    3K  0

    1991 Mitsubishi Eclipse GSX
    manual · 1G DSM
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  21. Blkapache01

    Blkapache01 Proven Member

    34
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    Joined Mar 28, 2017
    Birmingham, Alabama
    Ahh, man. I got in a tad bit too late...LOL. Thanks for the info, though. I'll look into it. Do you know offhand about how much an ECU repair runs or costs to look at it?

    Awesome. None of the TB bolts have straps to them so I'm gonna give that a remedy. Thanks.
     
    Last edited by a moderator: Nov 24, 2019

    Street Build 507  0

    1991 Eagle Talon N/T
    manual · 1G DSM
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  22. 1990TSIAWDTALON

    1990TSIAWDTALON Moderator

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    Independence, Kansas

    Street Build 3K  27

    1992 Eagle Talon TSi AWD
    awd · automatic · 1G DSM

    522  14

    1990 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM

    444  18

    1967 Chevrolet Camaro RS
    rwd · automatic · Misc Vehicles

    Street Build 642  4

    1998 Eagle Talon TSi
    fwd · manual · 2G DSM

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    1990 Eagle Talon TSi AWD
    13.620 @ 108.460 · 1G DSM
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  23. Blkapache01

    Blkapache01 Proven Member

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    Joined Mar 28, 2017
    Birmingham, Alabama
    Thanks for this info. As "fate would have it" mine does NOT have a ground strap at all. SMH... Do you know where I can get another one or is it ok to create a makeshift strap like a wire and clip on some ring connectors?
     

    Street Build 507  0

    1991 Eagle Talon N/T
    manual · 1G DSM
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  24. 1990TSIAWDTALON

    1990TSIAWDTALON Moderator

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    Just make your own ground and confirm it has continuity to the battery, not just the firewall or such. Then when it "clicks" to ground, the ECU sees that signal and knows you are at idle, or are supposed to be. Make sure the slight bit of slack is in your throttle cable and let the ECU do its work.
    Glad to be able to point you to a good thread. :thumb: Thats the whole idea for this "library" in a GREAT forum!

    Edit. You can ground to the closest ground point and check for a good ground. I don't go all the way to the battery with a dedicated wire, just ground the TB good so the sensors do their job. :)
    Marty
     

    Street Build 3K  27

    1992 Eagle Talon TSi AWD
    awd · automatic · 1G DSM

    522  14

    1990 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM

    444  18

    1967 Chevrolet Camaro RS
    rwd · automatic · Misc Vehicles

    Street Build 642  4

    1998 Eagle Talon TSi
    fwd · manual · 2G DSM

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    1990 Eagle Talon TSi AWD
    13.620 @ 108.460 · 1G DSM
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  25. 1990TSIAWDTALON

    1990TSIAWDTALON Moderator

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    If you find NO GROUND when you check, you may have to adjust the stop switch. It is a simple adjustment but only do it if you can confirm that it ISN'T working correctly. Ask for help if you need to, it's right here!
     

    Street Build 3K  27

    1992 Eagle Talon TSi AWD
    awd · automatic · 1G DSM

    522  14

    1990 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM

    444  18

    1967 Chevrolet Camaro RS
    rwd · automatic · Misc Vehicles

    Street Build 642  4

    1998 Eagle Talon TSi
    fwd · manual · 2G DSM

    Street Build 5K  11  25

    1990 Eagle Talon TSi AWD
    13.620 @ 108.460 · 1G DSM
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