DPS

Hello everyone. I took EFI 101 and Advanced at EFI University and I've been salivating over doing my first tune. I have many variables working against me with my first attempt. Here's the overview (what I've been told anyway):

'02 Firehawk M6
Dart Heads
Aftermarket Hydraulic Roller Cam (specs haven't been disclosed yet)
SLP Lid
"Modified" MAF
Headers


Heads and cam were just installed and the installer lashed the valves to 0 with no pre-load. This guy is respected in the F-Body world for doing cam specs and installing head and cam packages. There seems to be alot of valvetrain noise though. The SES light is on so I A-Tapped it and it's detecting an engine misfire. LTFTs at idle are approx. -17 on one bank and +15 on the other. Assuming that the knock sensor reports engine misfires, is it possible that the valve clatter could trip this? I was also told when I purchased Autotap that I would be able to view knock retard and it's not there.
I got really discouraged today (partially because of the difficulties I've had with my Innovate products, not to mention I couldn't open my A-Tap log file either) so if anybody can point me in the right direction I would really appreciate it.

dynocar

I would recommend having your valve lash adjusted to manufacturer's specs then see where you are at as far as misfires, fuel trims and valve train noise. Usually you are going around another problem, such as a mismatch in valve springs, proper spring shimming etc, if you need to "misadjust" with a zero lash proceedure. Your crank sensor, not your knock sensor, is used to detect misfires. Sometimes a radical cam that causes a rough idle will cause a misfire problem which is best solved by going into the PCM and tweeking the misfire detection tables. However, a noisy valve train could be picked up by the knock sensor causing spark retard and loss of performance. Especially when we go with internal engine mods, we really need to get things right both mechanically and PCM wise.

DPS

It is a fairly radical cam. If I knew that this was causing a misfire I would change the tables but I'm just afraid of covering up a legitimate problem. I'm trying to be very cautious. Why do you suppose the LTrims are completely opposite from bank 1 to bank 2? Thanks for the response.

dynocar

Some of many possibilites for bank to bank L Trim problems are, a constant misfire on one bank will cause that bank's O2 to read very lean, too low of an idle RPM will not keep your O2s hot enough especially with a cam and headers, O2s are too old or contaminated with soot from running too rich or from misfires and a header leak will cause such a problem. Like I previously stated, I would get that cam lashed in correctly first. With a radical cam you will need a higher idle RPM such as 900-1200 RPM. A pair of fresh O2s are a must for such applications. Hopefully you do not have an auto tranny because a tight stock like stall converter, wild cam and long tube headers can sometimes be a tuner's nightmare. They will not allow the idle RPM to be high enough causing misfires and cooling the O2s too much. On some cars I've had to run constant open loop to get by such a combination of problems or go to a less radical cam. Good luck.