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Thread: IAC & idle trouble again.

  1. #1
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    Default IAC & idle trouble again.

    Hi, I've read and tried a lot of the high/stuck idle problems, I've changed values on the Sniper that is related to idle & advanced idle, but still I have issues with sudden high idle. Only when I shut off & restart the engine the idle is back to normal, for a short period, before it's revving high again. Sometimes I can hear the idle air valve/port is sucking air like you wouldn't know and the IAC is at 0%. Other times the IAC just stays at 0%, but the engine is revving almost as it should, but the IAC Valve is doing nothing.

    I have attached datalogs of my last run when it suddenly revved really high =Sniper 0002. And a good run, Sniper 0001. I'm running 4 speed manual gearbox. 355 High compression (11.7:1), street/strip camshaft. Attachment 3131

  2. #2
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    You didn't post your Config File with your datalogs. Always post your Config File with your datalogs. My first thought would be a defective IAC. But there are some things I would change. Without knowing your settings, I would lower your IAC Hold Position, it's at 30% right now. At idle, your IAC Position is 9 to 10, open your throttle shafts a little to lower that. As it comes down to idle with the IAC at 0, the RPM looks like it drops below your Target Idle RPM and has to open up to bring the RPM back up. If you look at your Base Fuel Table in Graph format, you'll see you have a hole in your fuel curve above 50 kPa and in the lower RPM ranges. That is probably why it goes lean when you let the clutch out and give it a little throttle.
    Last edited by 81 TransAm; 05-13-2018 at 03:23 PM.

  3. #3
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    Sorry forgot to add the Config File, have attached them now. My IAC is actually 4-6% ish, I have a really hard throttle return spring, but still it won't return completely. If I manually push the last bit, not even noticeably, I can hear the engine calm down a few more RPM. Not much at all, not even easy to see on the display, but it's possible to hear. I've tried springs on top of the throttle bracket, and bottom as it is placed now, and both, and still it is not possible to get it 100%, the TPS isn't even moving, so the best result is the one possible, without having a ridiculous hard throttle pedal. Sometimes IAC is at 8-10%, sometimes it's at 4-6% (most of the time). Funny thing is, I have two more Snipers installed that's exactly the same as this unit. Here's my Config File: Attachment 3132

  4. #4
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    Have you checked to see if the butterflies are centered in the bore and are not binding? I would raise your "RPM Above Idle To Re-Enable Idle Control" to 300 to 400.

  5. #5
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    No, but I'll check asap. Didn't know that was an issue, will report back. I'll try to change it to 400 RPM.
    The "RPM Above Idle To Re-Enable Idle Control" option; is that a Sniper EFI software option? I can't find that on the 3.5" handheld?

  6. #6
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    http://documents.holley.com/199r11031r.pdf (Holley Sniper EFI Instruction Manual - "IAC Ramp Start", Pages 56 & 67)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, FRPP 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 tires.

  7. #7
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    Quote Originally Posted by 81 TransAm View Post
    Have you checked to see if the butterflies are centered in the bore and are not binding? I would raise your "RPM Above Idle To Re-Enable Idle Control" to 300 to 400.
    Quote Originally Posted by Danny Cabral View Post
    http://documents.holley.com/199r11031r.pdf (Holley Sniper EFI Instruction Manual - "IAC Ramp Start", Pages 56 & 67)
    I was thinking about the "RPM Above Idle To Re-Enable Idle Control". I can find this option in the Sniper EFI PC software, but not on my Sniper Display. Value is set to 100, but as TransAm said, I should try to up this to 300-400? I have tried to set the Hold Position lower, much lower, and IAC Ramp Start (RPM Above Idle) is played with a lot also. Still it will hang on idle, and IAC falls to 0% and does nothing.

  8. #8
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    Quote Originally Posted by fullthrottle View Post
    I was thinking about the "RPM Above Idle To Re-Enable Idle Control". I can find this option in the Sniper EFI PC software, but not on my Sniper Display.
    You're right, it's only in the Sniper EFI software (laptop/PC). Sorry for the confusion.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, FRPP 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 tires.

  9. #9
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    I have some more datalogs, at the end of each datalog, the idle messes up. Hope someone sees a pattern here. Haven't driven it yet after I changed the "RPM Above Idle To Re-Enable Idle Control" from 100 RPM to 300 RPM, so more datalogs will come. Attachment 3133. At Sniper_0004 about 680 seconds out, the idle went bad.
    Last edited by fullthrottle; 05-14-2018 at 10:55 AM.

  10. #10
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    The "idle messes up" doesn't tell us what we are looking for. But what I see is your TPS RoC dumps a lot of fuel when you move the throttle and then the AFR goes pig rich, probably flooding the engine.

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