Hello
I have a 1997 GMC Sierra with the L31 5.7 Vortec. Right now it is 0411 swapped, 24x swapped and I now have long tubes and dual 2.5 inch piping. No other major mods. I am trying to prepare it for more mods and learn a bit of tuning in the process, first.
The 0411 PCM swap went really well and the truck really seemed to benefit from it even with a stock tune.
I followed the GMTruckCentral 24x conversion writeup by Aloicious and Lextech to do the swap using EFI Connection?s parts. For the tune, I took the calibration from our 2002 Suburban with 5.3 and swapped all of my tables over from the Express van tune, wrote that to my PCM and fired it off. Ran horribly. After messing around with the tune for a bit, I figured out that it would only run stable with the injector bank select set to LS values. I ran with it like that for a little while (I realize I should have questioned it more but all of my research didn?t show anyone with that problem so I didn?t find a fix). I did not get a check engine light or misfire codes, however it would stumble if I revved it quickly in park.
Exhaust was changed from stock manifolds and cats with aftermarket 2.5 in H pipe and straight through mufflers to long tube headers, 2.5 in pipe with cutouts, no cats (temporarily) and H pipe with the same straight through mufflers. It?s all clamped together for now.
With my new exhaust on, I decided to start learning how to actually tune for it. I started scanning and realized it was pulling ridiculous amount of fuel and was very much down on power. I couldn?t think of any reason why it would be pulling so much fuel so I figured maybe the pcm was acting wonky. This is when I prepped an 02 Camaro tune with all of my tables to write into the pcm. I wrote it to the pcm and the fuel trims were more? normal? looking. However, now I would get misfire codes and could see the scan reading misfires on cyl 2, 3, 4 and 7. After searching for the cause I decided to swap my fuel injector wiring to how it was before the 24x swap and it ran a lot better, no more stumble with revs. I suspect the write up should not say to swap those wires, because my injector bank select table now works correctly, as in it now has to be set to sbc values for the engine to run stable.
After swapping those wires, the misfires did not go away and it still lacks power. Here is a list of things I?ve done:
New plugs, wires, swapped around coils, new fuel injectors, checked coil wiring, pretty sure my injector wiring is correct now although it is not how the write up says it should be, and I did a compression test (180 to 190 on all except cyl 1, which was 200)
My questions are,
What would cause fuel trims to be so negative with the Burb OS and ?normal? (if it is normal) with Camaro OS
Am I correct about the injector wiring not needing to be swapped for the 24x swap when already running the 0411
The burb OS did not throw misfire codes, and I can?t even scan/ log them when using that OS or plugging into the suburban itself, why would that be?
The misfiring cylinders are the same ones that are involved in the firing order swap from ls to sbc, so I wonder if it is software/tune based, what are your thoughts?
Sorry for the beefy post, but I?m trying to learn and I need help