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Thread: New startup won't idle down.

  1. #1
    Join Date
    Sep 2016
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    17

    Default New startup won't idle down.

    Hello. I just finished swapping over to the Terminator X system on my 6.0L LS and and having issues. The car starts, but runs between 2000 & 2500 RPM. It will not idle down. I verified the throttle body is completely closed and it still will not idle down. I checked all lines for an open vacuum port, but can't find any smoking gun. The engine was running fine before I made the swap, but I did make quite a few changes. I originally was running the MSD Atomic TBI on a Holley carb intake with a 6012 box for the ignition. I swapped to a stock LS3 manifold with stock LS3 injectors. I'm running a new Holley 92mm throttle body with new IAC & TPS. I went through the initial startup procedure and it fired right up, but will just run at about 2500 RPM. My fuel pressure was running at 59 psi before I tore down the old setup and didn't make any changes to the fuel system. I installed a new Holley fuel pressure sensor in the fuel rail, but I don't think it's working. Any ideas would be appreciated. Thanks.

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    25,129

    Default

    To eliminate the IAC valve as a problem, temporarily block off the IAC air inlet port with a strong piece of tape. Also, ensure the TPS Position returns to 0% at idle.
    http://forums.holley.com/showthread....neral-IAC-Info (General IAC Information - Read "IAC NOTES")
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  3. #3
    Join Date
    Sep 2016
    Posts
    17

    Default

    So remove the IAC and tape off the opening? I'll give that a try and see what happens. Thanks.

  4. #4
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    Dec 2009
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    Connecticut
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    I didn't say remove the IAC motor! Simply temporarily block off the IAC air inlet port with a strong piece of tape.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  5. #5
    Join Date
    Sep 2016
    Posts
    17

    Default

    OK so I tried taping over the IAC inlet port and it made no difference at all. It started up and ran at about 2000 RPM, then slowly increased to almost 3000 RPM. Any other thoughts?

  6. #6
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    25,129

    Default

    Then the engine is inhaling air from another source.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  7. #7
    Join Date
    May 2014
    Location
    Bostwick, GA
    Posts
    222

    Default

    Quote Originally Posted by Danny Cabral View Post
    Then the engine is inhaling air from another source.
    ^^^^ This.

  8. #8

    Default

    I still have the same issue. Holley tech gave up on it after sending me a new ECU and a new IAC. So remove your IAC and extend it by hand all the way and reinstall. This will plug off the opening without inserting any foreign objects into the throttle body. Do not plug the IAC in. Then adjust the throttle blade so the engine will run at a normal idle. If you can get it to run at a normal level the problem is probably the RPM start ramp in the program isn't ramping down. A lot of people are having this issue with the Terminator X ECUs.

  9. #9
    Join Date
    Dec 2009
    Location
    Connecticut
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    Default

    Quote Originally Posted by Phobos84 View Post
    So remove your IAC and extend it by hand all the way and reinstall. This will plug off the opening without inserting any foreign objects into the throttle body. Do not plug the IAC in. Then adjust the throttle blade so the engine will run at a normal idle.
    I do not suggest doing this. The IAC motor is easily damaged.
    IF you want to permanently eliminate the IAC motor (for whatever reason), this is the proper way:
    GM https://www.holley.com/products/fuel.../parts/543-123 (Holley EFI 543-123 IAC Plug)
    or
    Ford https://www.holley.com/products/fuel.../parts/112-560 (Holley EFI 112-560 IAC Block Off)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  10. #10

    Default

    Danny, you're correct. I don't recommend doing this to an IAC that you plan on reusing in the future. You can get old ones from most any salvage yard for less than $5.

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