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Thread: Can't get idle under 2500 on LS1.

  1. #21


    Thanks for your help. The part I don't understand is when I installed the new Holley IAC and started it the IAC percentage was between 50% and 70% and running fine all the way to operating temp. Then I shut it off and started it again. It started with a 50% IAC and dropped to 0% within a few seconds. I know I should just wait and send the ECU back to Holley. But part of me wants to switch the wiring around just to see what happens. I guess I'll just wait for either Scott or Matt from Holley to answer my email and send me a shipping label.

    Well I'm not 100%, but I think I have it figured out. After doing a little research I found out that on the Sloppy Mechanics page there where people talking about idle problems with a particular firmware update that was published on the Holley website in November. If you follow the Sloppy Mechanics YouTube channel he even made a video about it. To fix it in the video he went back to the older firmware version and the problem went away. What I did was just update the firmware again. Holley has since updated the firmware since my last download. Anyway so far with the new firmware the car idles as it should. IAC percentage is right where it should be and all is well. I just hope it stays that way.

  2. #22


    Just read through all this, thanks for the final update. Glad you got it figured out.

  3. #23


    Well just to update. The problem came back. Idle went over 3000 this time. So I sent the ECU back to Holley. Anyone have any idea how long it takes Holley to look at stuff like this? They have had it for two weeks now. I called yesterday and they told me it hasn't been looked at yet.

  4. #24


    Phobos84, please reply when you hear something back from Holley. I've been chasing similar idle issues since installing my Terminator X Max in June. Granted some issues of mine were self inflicted, but everything has been fixed or so we thought, and gone over several times. I now have a known very good tune in the ECU, but still will not idle. This is a DBW setup, but have tried a cable TB with no luck. I have a couple very good sources for help locally and so far they're scratching their heads. I believe we're going to try a different ECU on Sunday if schedules align.
    Last edited by Bracket Boy; 01-24-2020 at 08:01 AM.

  5. #25


    I somehow accidentally deleted my post. Anyway over three weeks now and nothing from Holley. If they come back and tell me that there isn't anything wrong with the ECU then the Terminator is going on eBay and I'll have to find a different option. I have exhausted every other option I have. But I'll keep everyone updated.

    UPDATE: So after I posted here I sent Scott at Holley an email asking for an update. I'll cut & paste his response that I just got.
    "Yes sir, I apologize. I could of swore I sent you an email explaining what was going on. Basically we put the ECU on the test engine and we saw some of the same problems we're having on the phone. They're trying to identify the problem. They believe that it's a problem with the ECU. In order to get you going, I'm going to just warranty you a new ECU. I've already put the order in and it should be leaving today."

  6. #26


    We had issues with a ground issue on our first Terminator X Max: We got a new ECU in about 5-6 days. All is well now.

  7. #27


    Well I got the new ECU from Holley. Still won't idle under 3000. I checked continuity on each wire going from the IAC to the ECU and everything looks normal. So I'm going to block off the IAC opening with a old junkyard valve and set the idle with the throttle blade screw and just be done with it. Getting this to work properly is beyond my ability. I called Holley tech again and they told me "good luck". So I guess I'm on my own. I wonder if I'd have these issues with Drive-By-Wire? I also wonder if I should request a refund from Holley. $1400 is a lot to spend on something that doesn't work.

  8. #28


    I just finished an experiment. Like I said, I wanted to try I extended a junk yard IAC by hand and put it in my throttle body. Then I plugged in the Holley IAC and zip tied it so it wouldn't flop around. Then I opened the throttle screw until the engine would idle just under 900 RPM. Then I'd rev the engine and watch the IAC. On the touchscreen display it shows IAC 100% and the actual IAC was all the way extended. Then it dropped down to 40% and it pulled in halfway. Then it slowly dropped down to 0% and the actual IAC was pulled in all the way. So if I'm understanding it properly, it's running backwards. To be honest other than being just a little hard to start cold it seems to run great without the IAC. So I'm leaving it this way. Someday I might try reversing polarity on the harness, but not now.

  9. #29
    Join Date
    Dec 2009


    See post #12.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 11.8:1 comp, TFS R-Series FTI ported intake, 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, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, 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 MT tires.

  10. #30


    Yup. Did that. All the wiring is correct and it does the same thing with three different IAC motors. But for whatever reason it runs the steppers backwards. It has Holley tech stumped too. The odd thing is it doesn't do it all the time. Sometimes it's normal, but most of the time it runs backwards.

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