misfire issue after 411 swap

[makoskey]

Heres the deal:

99 Tahoe 4x4. I have a 383 with a comp cam 218/224 with 1.6 rockers
495int/503exh 112LSA. Heads ported/bowl blended. LT headers. 2600 stall.New Maf, stock TB.

I am still in the process of tuning(with a big help from Justin at BlackBear Performance!) And all my LTFT are around 0 to -7 worst case.

Runs great but I have 1 problem now.

MISFIRE! It occurs when I go WOT. I checked out the high tables under misfire and they are all maxed(to not monitor misfires). Wideband says WOT around 12.5-14 AFR.
When this happens my trans does not shift from 2 to 3 at WOT. At least I assume that is the problem.

And before you ask..new plugs, wires, Accel dist. and crank relearn performed. No codes(except the flashing misfire at WOT).

I have down a search and I only saw a case of shutting down the misfire tables. But I really dont want to do that. Anyone have any ideas on how to fix this. Aside form going back to stock?:)

[Lextech]

How about putting it in Speed Density and turning off the MAF? Do the Auto VE and see what happens. Can you log Injector Duty Cycle? You may be running out of injector.

[makoskey]

Injector duty cycle at 120% at WOT..yikes! I havent done auto VE still getting familiar with EFILive. I will give auto VE a shot and see what happens.
Guess I will have to start looking for a marine intake.

[dc_justin]

Hey Mark,

Did the updated tune I sent you have any effect?

Justin

[makoskey]

Oh yes it did, in a positive way.I also found out my MAF was causing the low airflow issues not the Brake Booster like I thought. Now my LTFT are in the -7 to 0 area, even at a 75MPH cruise. WOT is just amazing now. There are a few spots which need attention. But I can handle that with auto VE.

Its this annoying misfire which is driving me nuts! I monitor misfire data on all 8 cylinders and they all show errors at WOT. It wouldnt bother me much but it is causing my WOT 2-3 shift to not happen(at least thats what I am assuming). Seems to bypass both RPM and VSS and keep going till redline. Thats even on the retune you sent.

I will collect more data this weekend and send it off to you to look at. Maybe you have a couple ideas??

Thanks for your time and help!

Mark