Troubleshooting misfire on 2022 6.2 trailboss

[Steve082884]

Hey all, my names Steve, I have a 2022 6.2 TrailBoss. 13k on it, decided to go and put a whipple on it. Long story short, while I was data logging I noticed the truck was randomly missing on all cylinders.. I’m new to this forum stuff so I’ll try and figure out where to post my concern. Thanks

 

[Gangly]

What codes are you getting?

Check your High Pressure Fuel Pump (HPFP) readings as well as MAP, MAF, IAT, etc. If you haven't had the setup tuned professionally, your fuel maps may be off. Check your S-Trim fuel readouts to see how much its adding or removing.

 

[Steve082884]

I purchased the Whipple tune, it has new MAF, new plugs, new upstream O2s.. smoke tested for vac leaks twice, found nothing, long term fuel numbers hang between +4 and +6.. No codes…. I had HP send me a spare stock ECU , and no difference. I even took the blower off this past weekend, put it back to stock, re uploaded stock tune and it does the same darn thing in stock formation… had I not seen it on the data log, the average person probably wouldn’t be able to pick up on the miss..
As soon as I go above roughly 20% throttle, miss clears out.. as soon as you power brake it, miss clears out.. it can idle all day long and not miss. I’ve plugged up evap purge incase that was opening, no change.. I’ve compared both the 3Bar and 4bar MAP values both with blower and without, and there are no spikes, I’ve watched TPS during the miss, no spike in value.. I’ve swapped 3 different style plugs, blower plugs and factory, no change, new set of Texas speed wires, no change…all of which Whipple tech told me to replace and myself darn well knowing it wasn’t gonna fix anything.
Also found out from Hp tuners, that now with the ECU unlocked, it can no longer be calibrated using GM tools, so I would have to purchase brand new ECU and have it programmed…No lifter noise, fresh oil change when I put blower on, and did it again 2 days ago, running mobile1 0w-20 and Wix filter. Both whipple and Hp have no further suggestions. I’m afraid it’s internal but not really sure what mechanically would cause a miss at such a light throttle load between 1100-1700rpm. I have yet to learn about the timing advancement with this motor, I wonder if cam actuator (if equipped) is floating the timing during that range.. definitely a head scratcher but I really appreciate your response. I wanted to run it this weekend with both crank case breathers plugged to see if it changes the numbers. Otherwise in order to take it back to dealer, I would have to purchase and program a brand new ECU. Thanks again for your time.

 

[Stormin08]

guessing the misfire is intermittent, (as in) differing cylinder throughout the range...varying when it does it ?
not the same pattern, each time ?
yet a miss just acting sporadic

 

[Steve082884]

Correct, eventually all cylinders record misfires. But like I mention, if I get into the throttle just a bit like I mean barely putting a load on it, miss goes away. Extremely odd, this one’s gonna lead me into an early retirement, lol.

 

[Gangly]

I wonder if your DFM is causing the misfire, and when you give it throttle it goes back to non-DFM and runs properly. That would explain the random misfires on multiple cylinders at zero/light throttle, and instantly going away when you give it throttle. I know my truck will slightly shake when DFM is active, but as soon as I give it even the slightest bit of throttle it smoothens out and runs perfect.

Also, check your motor mounts as they can be a source of false knock, and perceived tuning issues.

 

[Steve082884]

So apparently DFM gets disabled with whipple tune, so i compared 4 logs between whipple tune, factory tune, and factory tune utilizing pulsar LT both with and without DFM activated. And also whipple tune, piggybacking Pulsar, and every one does same thing. That’s why I was assuming mechanical. When it’s missing, nothing on knock data. I’ll check the motor mounts too , thanks for the help.