434ci 262/266..car breaks up under 3k then cleans up.

[Snyper]

The car runs awful under 3k....surges backfires and sometimes it sounds like I get an intake backfire....as soon as the car hits 3k it cleans right up and runs strong...I had a cracked plug and replaced all of the plugs with an .034 gap....Afr is on the 14s while cruising. Any ideas what would cause this? While it's surging it feels like the car is driving through mud.

[Snyper]

I made a long log today and im not sure if this means anything but I notice that when im starting off from a stop(which is when the car breaks up so bad its almost un drivable and I have to ride the shit out of my clutch) that it seems to be pulling timing from a weird area that my normal LS2 didnt.. heres a picture of it... in the .52-60 range when I start off around 800-1200 theres no timing in there...Heres the log and the tune..

[Z06-Hammer]

Don't look like its pulling timing but what your commanding from your High Octane table.

[Snyper]

Yeah exactly. My stock LS2 wouldn't use that section of the Table when starting from a stop. This thing draws way more air than it did. I'm hoping this is the cause of the awful bucking as I start.

[Snyper]

Well I got that sort of sorted out. It takes off much better now. However the car surges horribly until 3k still and then its like nothing every happend. I can even hear it backfiring out of the intake. I took away 5* of timing in those areas and added back 15..just to see if either would help and nothing makes a difference..heres a log of what its doing.. The more load I put on it the worse it gets and you can see the timing go very jagged..

[IDRIVEAG8GT]

Ah, I have this issue too only it's intermittent. I usually rid the vehicle of the problem by performing a Write Entire. They just get pissed off after being written so many times.

[Snyper]

I can't figure out what is causing this. It runs good from 1-2k from 2-3 it backfires surges and pops, then from 3k up it runs absolutely perfect.

[IDRIVEAG8GT]

You have spark smoothing enabled?

[DSteck]

What kind of plugs?

[Snyper]

Ngk Br7ef @ 34

[Snyper]

Ive taken away up to or plus 10* of timing from the problem areas with no luck as well...When I put load on the engine the timing gets very jagged...

[IDRIVEAG8GT]

Apparently my posts are sub-informative.

[Snyper]

Explain?

[Mep_q8]

Try interpolating vertically the areas between 2000 & 3600rpm and map areas of 60 till 110kpa. If your running in true SD, those maps look very spikey for the motor to run smoothly at that rpm point. Give it a try and see what happens.

[Snyper]

Does it in Maf mode too.

[Snyper]

What kind of plugs?

BINGO! I was running BR7EFs gapped at .032. I switched back to TR6s and gapped them at .044 and the problem is completely gone. Not only that but the car feels like it picked up 50+hp. One thing that changed dramatically is that WOT AFR has always been 12.5 or so and would settle down to 12.1 by 7k. A simple plug changed managed to make the WOT AFR shoot to 15.2 requiring me to add MUCH more fuel up top. Could this be from the fowled plug?