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Thread: Not coming back to idle.

  1. #1

    Default Not coming back to idle.

    For some reason, the Sniper EFI I installed about six or seven months ago is not coming back to idle. If I blip the throttle, it will return. I thought it might be a linkage issue, so I disconnected the linkage and it made no difference. I then thought I might have some dirt or something around the throttle shafts and sprayed them profusely with carb cleaner, both inside and out. It's been working great since the install, but now it's acting up. Could it be a computer setting I need to check? I also noticed the idle on the handheld shows around 950 idle RPM. I have the Sniper set at 850.
    Last edited by RBolig; 09-17-2019 at 05:25 PM.

  2. #2
    Join Date
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    The idle speed screw/IAC Position % relationship must be properly set for idle control. Ensure the idle speed screw on throttle body, is adjusted to achieve an IAC Position of about 5-10% at hot idle.
    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, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 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/2800 RPM converter, M4602G aluminum driveshaft, 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.

  3. #3

    Default

    Danny, IAC is at 5% at hot idle. It idles fine. The issue arises when I apply throttle. If I take the engine to 2,000 - 2,500 RPM & release, it doesn't return to idle. It wants to remain high until I blip the throttle. It's weird, it just started acting up after several months of working great.
    Last edited by RBolig; 09-17-2019 at 10:02 PM. Reason: Typo

  4. #4
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    Ensure the throttle shafts/blades are fully returning to the idle position when this occurs.
    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, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 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/2800 RPM converter, M4602G aluminum driveshaft, 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.

  5. #5

    Default

    RBolig as in Randy Bolig?

    First thing to do is to figure out if you have a hardware problem or a software problem. (This is always the first thing to figure out with a Sniper, since it is a mixture of HW & SW. Lots of people never understand this part since they are old time car guys who have never encountered a SW problem.)

    Like Danny says, first check to see if you have any mechanical problems. If you don't have a mechanical problem then turn on your ignition, start the datalogger and fire up the engine. Watch the monitor and see what's going on. If the Sniper worked fine before, but doesn't now then that indicates a part failure. Most likely the IAC, but it could be something else. If you haven't change the program then it shouldn't be a setting change.

  6. #6

    Default

    Andy, you are correct. It's been a while, hasn't it? I disconnected the linkage and confirmed the throttle shafts are returning to the home position. I changed nothing as far as settings. How do I test the IAC?

  7. #7
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    Did you check the secondary shafts?

  8. #8

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    Yes sir, I did.

  9. #9
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    When it acts up, did you cover the IAC port to make sure it's not sticking. Check it when it's operating correctly, so you have something to compare it to.

  10. #10

    Default

    Quote Originally Posted by RBolig View Post
    Andy, you are correct. It's been a while, hasn't it? I disconnected the linkage and confirmed the throttle shafts are returning to the home position. I changed nothing as far as settings. How do I test the IAC?
    I think you've already tested the IAC and it failed, but you can do some more testing to confirm it's the problem. Are you working with a laptop or just the handheld? Things are easier with a laptop, but you can do the same thing with a handheld. One test is to change the idle speed and see if the IAC can control it. Raise the speed several times and then lower it several times and see if the IAC is making the adjustments.

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