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Thread: Sniper misfiring & extremely weak under load.

  1. #1

    Default Sniper misfiring & extremely weak under load.

    I have a Holley Sniper EFI on a 454 with stock internals & heads running a dual sync distributor with timing control as well. My Sniper will cut out under a load or any mid to heavy acceleration, while going down road about 2200 RPM. All it does is run rich and just stumble when the issue occurs. I've installed new fuel pump & filters along with TPS checked all vacuum connections as well, and made sure my SD card contents are up to date. I've talked with Holley Tech and they are just as puzzled as I am. Any help would be really appreciated!

  2. #2
    Join Date
    Nov 2014
    Location
    Ont. Canada
    Posts
    639

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    Have you checked your plugs? It's real easy to foul a set of plugs with a rich startup.

  3. #3

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    Yes, I've checked those, surprisingly the plugs looked great. I also replaced the WBO2 sensor. The only thing I can come up with is bad Learns possibly?

  4. #4

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    I had a similar issue where every time I reached 2200-2500 RPM, it would cut out really bad. I disconnected the battery let it sit for 20 minutes. While I waited, I completely deleted everything on the SD card, and then re downloaded the SD card contents, and the same Global Config File/Tune. I then re-uploaded the Global File, and the problem has been gone ever since. The strange thing is that I never changed anything with the tune. It was like a glitch.
    Last edited by ChevyC10; 02-21-2018 at 08:28 PM.

  5. #5

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    I will try that tomorrow and see how it works. Thank you for the advice.

  6. #6

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    Have you checked actual fuel PSI? The internal regulator may be faulty.

  7. #7
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    17,637

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    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  8. #8

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    Fuel pressure checked out. The problem was an EFI software glitch caused from bad Learning. I went through the setup Wizard again, the issue was corrected after that. Thanks for the help though!

  9. #9

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    Glad it was an easy fix. Thank you for keeping us updated.

  10. #10
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    17,637

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    Quote Originally Posted by 454fanatic View Post
    The problem was an EFI software glitch caused from bad Learning. I went through the setup Wizard again, the issue was corrected after that. Thanks for the help though!
    Read 6th paragraph: http://forums.holley.com/showthread....2523#post62523 (Holley EFI Tuning Tips & Information)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

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