queso

I already searched P0300 and Misfire. All info found is about miss & lack of power at high RPM's...Mine is the OPPOSITE!! Can someone gimme a hand with some ideas?

Car is 2002 TA, M6. Professionally tuned for a 224/224 .581 112LSA and longtubes. Car ran great.

Just finished installing Stage II heads and it fired up on 1st try. Idles OK, oil press at 40 psi at idle, no ticking, looks good. I also changed the injectors to Racetronix 37# which are like 43 lbs at 58psi. So, I bumped up my IFR table by 150% with LSEdit and nothing else. Added a set of Yella Terras and Comp Lifters (bolted them up to 24 ft/lbs).

I've already seen my LTFT's out of whack. Bank1 is at +23 and Bank 2 is at +15. So I guess i've messed up the O2's with coolant that ran down the header pipes when we popped off the heads. Will change those immediately.

Here's what's wierd. It drives like it's on 7 cylinders (chug..chug..chug) until it hits 3500 RPM. Between 3000 - 3500 you feel that extra cylinder intermittently kicking in, after 3500 ~ 4000 it all cyls fire perfect and the car goes like a bat outa hell.

Logged with EFILive and have:

Cyl 1 Misfire History - 438 <------ yikes!
Cyl 2 Misfire History - 27
Cyl 3 Misfire History - 2837 <------ big yikes!
Cyl 4 Misfire History - 70 <------ smaller yikes!
Cyl 5 Misfire History - 23
Cyl 6 Misfire History - 9
Cyl 7 Misfire History - 9
Cyl 8 Misfire History - 11

Aside from wires, plugs, and O2's, what else to check ?

JoeyGC5

iTrader: (24)

Check the injector/coil harness for frays or bad connections. Ohm the injectors and see if there might be one at a higher resistance than the others. Retune

queso

OK. By reading everything I could find on Misfire's and injectors, I reached the conclusion that what will cause LOW RPM misfires and be OK at higher RPM's is the Injector Offset. The way I understand it, is that the Racetronix being much larger than stock, the computer is telling the injectors to open and close for so little time, that they sometimes actually never have time to open at all, because the amount of time commanded is smaller that the actual time it takes for them to open and close. This has the effect of starving the cyl of gas often enough that it is detected as a misfire.

So, I think that by increasing the Offset, it allowed more time to allow the injectors to open and spray gas before closing. Now the question is how much more?

I tried three values from baseline stock values, here's what happened:

1) Mult Inj Offset table by 110% - Misfire numbers came down SIGNIFICANTLY, but #3 is still high 1,230 misfires counted, all others are around 10 -20. NO backfires.

2) Mult Inj Offset table by 115% - All came down to zero except #3, which did some 70 misfires. But now I have backfiring when coming off the accelerator and any RPMs.

3) Mult Inj Offset table by 113% - #3 went to 430 misfires, and backfires are less.

Now, I'm really gonna need help from someone who's done these before. Or maybe, the folks at RACETRONIX can use some of the money I forked over for these injectors kindly have someone reply with some information or suggestions.

I'm not trying to become an expert or a tuner or anything like that. But I've put my honest effort into this and basically I just want the car to run sufficiently well to drive 130 miles to Tampa and have it professionally tuned again...

PREDATOR-Z

Post in the tuning section. Have you tried a PM Racetronix

queso

Trying just that...

Nate_Taufer

iTrader: (1)

check #3 rocker and pushrod. Could be just something loose. Also pull the plug for #3 if all other cylinders are operating okay. Could of fouled the plug from all the unburnt fuel at low rpms. I would actually change out all the plugs to be safe.

Good luck with your setup.

Nate