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Thread: Sniper & Dual Sync hard acceleration fails.

  1. #1

    Unhappy Sniper & Dual Sync hard acceleration fails.

    Hello Holley forum folks. I have been reading the forum for about 3 years, but this is my first post. Three years ago my son & I built a 350 Chevy for my late fathers 1995 C1500. But I'm honestly at my wits end and cannot get the Sniper EFI to run right. We researched and read a lot and this is the build:
    GM performance ZZ4 short block with forged crank/rods
    Rattler 7 1/4 balancer
    Trick Flow Super 23 175 heads
    Full roller rockers 1.5 ratio
    Holley Sniper 4150 TBI
    Holley Dual Sync distributor
    MSD street fire CD box
    1-5/8 headers 3 inch collector
    3 inch exhaust
    Holley Sniper intake
    1800-6800 intake
    Edelbrock Rolling Thunder cam
    280°/290° int/exh
    .469"/.479" int/exh
    4L80E full manual valve body
    3:73 limited slip

    After getting the engine broke in when I stomp on the gas it falls on its face. Gradual acceleration is fine. I've been trying to tune the Sniper for two years (as time permits). We've read and followed the directions for everything to exact detail. I've been reading the posts in the forum tirelessly, but I cannot get it to run the way it should when I hit the gas hard it stumbles and if I let off it recovers. I've a datalog file that I took today and was wondering if the experts here can take a look please?
    Attached Files Attached Files
    Leviticus 17:11

  2. #2


    Can you post the Config File too? I'd recommend the HyperSpark distributor. Throw it in, verify timing, done.

  3. #3
    Join Date
    Dec 2009


    Pay special attention to the center paragraph in blue print:
    Originally Posted by Danny Cabral
    Quick Datalogger Information:
    Always provide data, not just symptoms. Is the AFR & ignition timing optimized? Overlay the datalog onto your Config File.
    Ensure the Target A/F Ratio table is properly programmed for your engine. Ensure the ECU is "Learning" (Learn Table LINK).
    Scroll through the datalog to the problem area. Then look exactly where this happens on the Base Fuel & Timing Tables. Scrutinize:
    RPM, MAP, MAT, TPS, CTS, IAC, Target AFR, AFR Left, CL Comp, Ignition Timing, Duty Cycle, Fuel Flow, Fuel Pressure & Battery.

    Using the Holley Sniper EFI software (LINK), look at where the live cursor moves to during this occurrence, and
    manually tune that area of the Base Fuel Table (enrich or lean) & Base Timing Table (optimize ignition timing).

    I find the most helpful datalog function, is overlaying the datalog on your Config File.
    I'm in the habit of using the datalog Overlay feature every time I review a datalog.
    Click on "Datalog" (on the top Toolbar), "Activate Overlay", then "Open Data Log".
    You can literally "playback" a recorded event, and watch it as it happened on any screen.
    Minimize (shrink) the datalog window, and move it to the bottom of any Config File screen.
    Then click & scroll anywhere on the datalog, and watch it playback on your Config File (EFI software). (Holley EFI Datalogger Instructions) (Datalog Information - Read "NOTES") (How To Record & Email A Datalog) (Closed Loop Datalog Tuning - Posts #2, #4 & #6)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, 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, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, 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 M/T Street Comp tires.

  4. #4


    Post your Config File. From what I can see in the datalog I'd say your tune is wrong. 10° of timing is too low for that cam, and 14:1 AFR is too lean when you're accelerating. Fix your tune and it'll probably run just fine. You probably have other issues in the tune, but you need to post the Config File before anyone can help you.

    I agree that the dual sync was a bad choice for that engine, but since you have it you can use it. It's just bigger and more expensive and has more features than what you need. But if you built the engine a couple of years ago the HyperSpark might not have existed then.

  5. #5


    So I got curious and went through the datalogs. You have some EMI issues. When you have some of these lean spikes you're losing major data points when they occur in some areas. I'd go over your wiring and make sure all grounds and connections are good & clean.

  6. #6


    EMI could cause the issue I suppose. Perhaps some of the Sniper wiring is crossing the spark plug wires, and under hard acceleration the voltage is jumping across the wires and causing the Sniper to reset.

  7. #7
    Join Date
    Feb 2020
    Wheeling, WV


    Ya, show us your GFC. I just took a peek and my first thought about your expressed problem only is this, your Acceleration Enrichment is way off. Let us see your GCF and I'll give you a few ideas on what to try. Has it ever accelerated properly?

  8. #8


    Thanks for all the replies folks. I found out one of the poly locks on a rocker backed way off and the intake valve on #3 wasn't opening. I also found a broken damper spring. So I'm gonna install some stiffer springs and some stud girdles. Thanks for all the advice. Oh, I'm gonna clean up the wiring a bit as well. Once I get all this done I'll come back and update the thread with what's happening. Thanks again.
    Leviticus 17:11

  9. #9


    Quote Originally Posted by 1711 Customs View Post
    I also found a broken damper spring.
    That's what happened to me and pushed me to go with the Sniper...and a ProCharger. I'm sure you know to spec the spring pressure for the cam. Glad you got it figured out!

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