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Thread: Rough idle & IAC all over the place.

  1. #11

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    Quote Originally Posted by EDW821 View Post
    I've been experiencing high idle not right after startup, but 20 seconds after startup, not as it was right after. I wonder what could cause this. The IAC is increasing as well, just like it was immediately after startup.
    Check the idle vs engine temperature settings with the handheld or the Sniper EFI software.

  2. #12
    Join Date
    Dec 2009
    Location
    Connecticut
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    23,085

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    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. #13

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    Wanted to share this experience for anyone else that might have similar issue. I had installed the Sniper about 8 months ago, it seemed better at first, but over time got worse & worse. Learning just made things worse and I'd reset with the Wizard and things were a little better, but never back to that first day experience.

    So I was done, I was going back to my Carb and just call it lesson learned. I put a NEW Holley carb back on an engine that was 8 months old and the darn thing would not idle down. Yes, I know how to adjust a Holley carb before you comment, and I knew this issue, it was a major vacuum leak. I've seen it many times, but where could it be coming from. I decided it had to be on the intake, and yes it was. I removed the intake and I could see the vee pattern at several locations where dirty air was being drawn into the engine.

    I replaced the intake gaskets, installed the carb and the engine idled was down to 500 RPM on a mild cam engine and purrrrring like a new car, unreal. So...I thought, maybe this was my issue with the Sniper. Had to be, the leak was so large that it could not tune a good AFR and that's why I had so many issues.

    Well, I replaced the Holley and started the car, for a few moments it seemed OK then quickly went back to running bad. Said I'm done with this, put the carb back on and WHATS THIS! Won't idle down again and rough, another vacuum leak?

    Yes it was. I pulled the intake again and sure enough I had take out the new gasket in several locations. I replaced again, and this time I just left the carb on the engine and running fine. I've installed intake gaskets and I know how to torque. However, for some reason when I put the Sniper on the engine it seems to take out the intake gasket. My guess and I'm open to suggestions is that the Sniper restricts so much at idle in order to use the IAC that it's causing too much stress on a new/rebuild engine. After all I don't know how many times the heads have been reworked and not being brand new the tolerance may not be as tight as a factory new engine. Any comments or thoughts?

  4. #14
    Join Date
    Dec 2009
    Location
    Connecticut
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    23,085

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    Quote Originally Posted by eDecisions View Post
    I've installed intake gaskets and I know how to torque.
    It's not a torque issue. It may be a intake manifold machining/fitment issue.


    However, for some reason when I put the Sniper on the engine it seems to take out the intake gasket. My guess and I'm open to suggestions is that the Sniper restricts so much at idle in order to use the IAC that it's causing too much stress on a new/rebuild engine.
    No.
    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. #15

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    While I'll agree with Danny that the Sniper IAC isn't causing restriction problems, I have seen an engine go from idling rather nicely at 650 RPM pulling 18" vacuum with a QuadraJet, to idling even better at 650 RPM pulling 20-21" vacuum with a Sniper. I'm betting that either the heads of manifold aren't perfectly flat, and the Sniper makes enough better vacuum to pull the gasket. I've also seen enough paper intake gaskets get moved around, that I only use the nice Fel-Pro ones with the metal layer - they don't move.

  6. #16
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    23,085

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    21 inHg of vacuum should not pull any type of intake gasket out of place. There's something wrong with how the intake manifold mates to the cylinder heads. It's not uncommon.
    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.

  7. #17

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    eDecisions, when you say the engine was "8 months old" does that mean you had it rebuilt? If so, did they deck the block?
    69 Camaro
    400 SBC, ProCharger D1SC

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