Frustrating Intermittent Misfire

[Dex]

I can tell you I was battling the same thing for the past two months. I back dated to V110 and it went away. No miss in two weeks. You can save your existing tune prior to the back date, and reload it once you have the firmware done.

I'm having a similar problem as well. It looks like there's a V4 110 & V5 110, which one did you go with? I had a 100 mile drive to cruising the coast and it must have happened about ten times during the drive mainly during steady driving. It does happen every now & then while accelerating, but not that often. It seems to have gotten worse after installing the Dual Sync distributor, switching to sequential injection, and updating firmware. It feels & sounds like the engine shuts down for about a half second and then runs fine. It's pretty abrupt when in overdrive and lockup as it bangs the gears hard.

[Zappa]

...it does happen every now & then while accelerating, but not that often. It feels & sounds like the engine shuts down for about a half second and then runs fine.

This is the EXACT same symptom I have and I can actually watch it drop almost exactly 500 RPM when it does it, this only started after upgrading to V6 110 firmware. Note: I'm running the MSD GM EFI Pro-Billet Distributor. (https://www.holley.com/products/igni...let/parts/8366) I'm really interested to see if anyone from Holley is across or aware of this? Or if they can provide some insight into why this may be happening?

[Dex]

Sorry you're having this problem also, but I'm glad to see I'm not the only one. I'm running V5 170 right now and was waiting to see if someone suggested what version to go back to before I did that. If anyone from Holley is looking into this problem, it seems in my case that it happens mostly when trying to stay a steady speed by making very very slight throttle adjustments. Mostly when just barely letting off the gas like only 1% TPS or less. Any help is greatly appreciated.

[Fgreen426]

Right before I started having the issue I got a new Laptop. Without realizing there was a update, I downloaded V5 171. Didn't think nothing of it. Didn't notice the miss at home, then drove north 800 miles to go on the Hot Rod Power Tour. It was hit & miss if it would do it. Changed MAP and crank sensor, since I was noticing a relation on datalogs. No change. Then I remembered I changed EFI software before leaving home. I went back to V5 110. I haven't had the miss in a month and I drive every day to work in it.

[Dex]

Thank you so much for making that post. I've been dealing with this problem for months, but it was so intermittent that I couldn't catch it happening on a datalog. I switched to V5 110 Sunday and drove it to work twice and no misfire yet. The real test will be taking it on the interstate for a good drive, but I think it's fixed. Thanks again for your feedback.

[Danny Cabral]

Note: I'm running the MSD GM EFI Pro-Billet Distributor. (https://www.holley.com/products/igni...let/parts/8366)

See post #2.

[AndyF]

Right before I started having the issue I got a new Laptop. Without realizing there was a update, I downloaded V5 171. Didn't think nothing of it. Didn't notice the miss at home, then drove north 800 miles to go on the Hot Rod Power Tour. It was hit & miss if it would do it. Changed MAP and crank sensor, since I was noticing a relation on datalogs. No change. Then I remembered I changed EFI software before leaving home. I went back to V5 110. I haven't had the miss in a month and I drive every day to work in it.

That's kind of spooky, but very possible. Once a SW package gets complex enough, then ghosts appear in the machine. We might never know what the problem is. I used to work at Xerox and we had rooms full of electrical engineers with printers hooked up to million dollar machines sniffing away for random errors. There was always a reason for the random errors, but sometimes it took weeks for those guys to sniff it out. Some of the time it was a simple "oops, forgot about the line of code" kind of stuff. Often as not it was something that our buddies at Microsoft had screwed up inside Windows. Most of our software bugs came from bugs inside of Windows. HEFI could be the same way.

[Danny Cabral]

Right before I started having the issue I got a new Laptop. Without realizing there was a update, I downloaded V5 171. Didn't think nothing of it. Didn't notice the miss at home, then drove north 800 miles to go on the Hot Rod Power Tour. It was hit & miss if it would do it. Changed MAP and crank sensor, since I was noticing a relation on datalogs. No change. Then I remembered I changed EFI software before leaving home. I went back to V5 110. I haven't had the miss in a month and I drive every day to work in it.

If you look at the Holley EFI V5 Revision Log, V5 Build 171 EFI software is not compatible with V5 Build 110 ECU firmware.
As I always say, "The EFI (laptop/PC) software, ECU firmware & touchscreen unit must all be version compatible (LINK)."

[alan91z28]

How did this swap go? Did it resolve the intermittent misfire?

Sorry, I don't really post here anymore, I just happened to check to see if anything new was going on since I haven't checked since June.

I hate to say it, but I just couldn't put up with this poor operation of intermittent misfires. Over the July 4th weekend I ripped out the Holley HP and put back in basically the old GM ECM type (7730 with Flash from Dynamic EFI). In two days I had it driving better than I ever had with Holley. Zero problems and no intermittent misfires. I have driven it now several thousand miles without any repeat issue.

The Holley has a lot of great features that I really liked, but I just couldn't put up with this issue. Spent a lot of money and time, not bitter about it, but I won't ever use an aftermarket ECU again on any project. I'm going to standardize on using the GM 411 on all my future projects.

[Fgreen426]

If you look at the Holley EFI V5 Revision Log, V5 Build 171 EFI software is not compatible with V5 Build 110 ECU firmware.
As I always say, "The EFI (laptop/PC) software, ECU firmware & touchscreen unit must all be version compatible (LINK)."

I meant to say Firmware. I had all systems running the V5 171, when I back dated firmware & software to the V5 110, this misfire went away. 3000 miles with no issue since.