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Thread: V5 Build 171 Skip/Misfire

  1. #1

    Default V5 Build 171 Skip/Misfire

    Another V5 Build 171 skip story. The specifics: Flying Magnet, Hall-Effect crank trigger, Magnetic cam sensor, COP ignition. Loaded V5 Build 171 (latest must be best, right?) over winter along with some other changes (kept the same Global Files). I have been chasing a random skip for last month. I finally read back through older forums, should have done it earlier. Reloaded V5 Build 110 firmware, all better. I'm posting this mainly to keep the topic "current". Interestingly enough, 110 is available again in the EFI software library. Perhaps there should be a "sticky" warning about this "small quirk".

  2. #2
    Join Date
    Sep 2015
    Greensboro, NC


    Thanks for bringing this up. In the past, I've had many issues with intermittent ignition misfires, but with the help of AndrewB70 got 99.9% of the issues fixed. Except for an annoying random misfire that would happen just as you described. Once a day, once a week, twice a day, totally random. It's like the ECU just blips for a brief second and picks up exactly where it left off. I checked and rechecked everything and never could catch it in the datalogs. A couple of months ago, after reading about similar issues on this forum I went back to V5 build 110 and so far so good. Ignition is Holley 565-202 Dual Sync distributor and a MSD 6A box & Blaster HVC-2 coil. Thanks - Shannon

  3. #3


    Same here guys. I chased this the whole last season. Have it in a jet propelled boat application so it's very obvious and easy to hear every event no matter how small, being I'm always under significant load when cruising. Could go 20 minutes without and than could start happening every few seconds. I also have caught it many times in datalogs. Basically the datalog keeps recording and there's a lean spike on both WBO2, RPM fall & recover quickly. Basically it looks like there's no fire from sparks based on looking at datalogs. Fuel Flow still shows consistent, naturally following the RPM as do all injector pulse times, etc. I also backdated to 110 having 171 previously, and it's been flawless since! Has anyone here have had these issues with V6, or I should ask has anyone solved this issue by updating to V6?

  4. #4


    I have a customer with an 8 second drag car that has a problem with random engine shutoffs. The engine will shut off for a tenth of a second and then come back on. When that happens he loses his race, so the issue is very annoying. We've chased a few things around, but I'm starting to think about downgrading him from 171 to an earlier version. The car ran fine with 140 in it, so we might go back to that. I wonder if anyone at Holley knows what's causing this issue?

  5. #5
    Join Date
    Dec 2009


    AndyF, what does his ignition system consist of?
    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, R134a 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.

  6. #6


    Quote Originally Posted by Danny Cabral View Post
    AndyF, what does his ignition system consist of?
    Dual Sync distributor with a MSD 7AL ignition box and a MSD coil. The datalogs are fairly clear that the ignition shuts off for just a beat then it comes back on. The other traces look okay. Sometimes the driver says the engine missed a beat, sometimes he doesn't even notice it, but it shows up on the datalogger and the car slows down by bit. We've swapped parts and triple checked wiring. The problem is very random. Sometimes he can make a bunch of passes with no problem and then sometimes it happens a couple of times in a row. The team has another car using the same ignition setup, but running V5 Build140 and it never has the drop out issue. So that makes me wonder a bit.

  7. #7


    I had this exact same saga and frustration last year using the Holley HP. Here's a link to my experience and similar data captures & conclusions. I got to the point I had changed wiring in the harness, spark plugs, plug wires, multiple ICMs, as well as GM HEI Small Cap to Holley Dual Sync/MSD CDI Box. I had sent this in last summer to Holley, but they would not even acknowledge back to me any reply despite several attempts on my part. I gave up and went back to OEM type ECM.

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