24x and stubborn misfires

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

Im sorry i havent read fully through this im at work.

Did you swap injector AND coil wires? I believe you need to swap both power and grounds.

Bank select should 01101001

The coils are wired up according to the info in multiple write ups, each cylinder going to its respective LS pin designation with 2, 3 and 4, 7 swapped. I swapped them again to see what would happen and it shook like crazy so I put it back. Think that's sorted.
The injector wiring confused me because the wire said to swap those but it misses worse when I do, and since the firing order is hardwired in the pcm, and I already was running with that pcm, my wiring would have already been correctly swapped when I converted to the 0411.

Each bank has it's own ground that the coils share. I'm at work rn as well so I cant check my bank table but its copied from the Express van calibration.

Quote:

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Originally Posted by anniversaryss

Im sorry i havent read fully through this im at work.

Did you swap injector AND coil wires? I believe you need to swap both power and grounds.

Bank select should 01101001

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Checked my bank select to make sure, and those are the values I'm running

What coils are you using?

They are the round body truck coils, I believe d585 is the number for them

The one log i looked at the one cylinder had over 5 thousand history misfires i would start there.
Its very odd. The main changes in the tune are correct. Typically you have to swap the coil AND injector wires so that is confusing as well.

This is from the gmtruckcentral writeup, implying i should indeed swap the injector wires at the pcm for 2 and 3, and 4 and 7 but when i do that it wont run with the inj bank select set to SBC values, only LS values, and it misses and shakes when i rev it quickly in neutral/park. Confuses me.

"However if you have an L31, you’ll just need to swap the pins for the injector controls at the PCM, if you have a 411 already installed, you need to Switch the wires of (C1-3 and C1-4) and (C1-43 and C1-44), if you don’t have the 411 installed, shame on you, and you’ll need to find your specific schematics for the proper pinouts."

I guess my main question is if the log/tune would lead you to believe it was tuning or something mechanical. And why I cant swap those wires like the writeup says!

Ok heres what i get looking at the injector schematics from a 96-97 v8. You swapped to the 0411 so youll be using the red/blue connectors.

Based on an fbody ls1 the blue connector has the injector wiring.


So with the injectors 2 and 3 then 4 and 7 swapped i came up with

Ls1 blue

Injector
1 pin 36 gets red 3 from truck
2 pin 4 gets red 32 from truck
3 pin 3 gets red 11 from truck
4 pin 44 gets red 12 from truck
5 pin 76 gets red 15 from truck
6 pin 37 gets red 16 from truck
7 pin 43 gets red 31 from truck
8 pin 77 gets blue 5 from truck

Does this sound right to you?

I found my old 0411 swap sheets from Lextech and it shows the same corresponding wire values for each cyl as what you wrote, and the same connector color, however compared to what you wrote 2 and 3, and 4 and 7 are swapped. When I have it wired the swap sheet way my SBC inj bank will work. When I wire it the way you posted, I have to use LSx inj bank select, but it will stumble on a quick blip of the throttle. With the SBC inj bank select, the fuel trims will go haywire.

Quote:

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Originally Posted by TheWildWolverine

I found my old 0411 swap sheets from Lextech and it shows the same corresponding wire values for each cyl as what you wrote, and the same connector color, however compared to what you wrote 2 and 3, and 4 and 7 are swapped. When I have it wired the swap sheet way my SBC inj bank will work. When I wire it the way you posted, I have to use LSx inj bank select, but it will stumble on a quick blip of the throttle. With the SBC inj bank select, the fuel trims will go haywire.

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Ok so with it wired my way and using the ls1 injector bank select are you fuel trims opposite? Like one bank pulling fuel the other bank adding or being much less?

With the SBC bank select what do you mean by "haywire"?

Which one of your logs represent the injectors swapped like mine and using the SBC bank select?

Both of these logs are with it wired your way, with different inj bank selects

Quote:

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Originally Posted by TheWildWolverine

Both of these logs are with it wired your way, with different inj bank selects

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Yep thats truly confusing. The trims seen with the SBC bank select is what would be indicative of an incorrect bank select. The LSX bank select was what id consider normal.

I guess if it works, it works, bow just to figure out that misfire.

I agree. I'm stumped on that one.

For the misfires, I'll try to outline the scenario again just to help organize my own thought process

Cylinders 2, 3, 4, and 7. I find it interesting that its the ones involved in the firing order swap
Cylinders 2, 3, and 7 seem to be somewhat similar in misfire frequency when you take cyl 4 into account as an outlier. Its much higher.
Cylinder number 4 I believe has/had a ticking lifter, I have not heard it recently so I don't know what to make of that.

Things I've done/tested:
New plugs
Tested plug wires, all are .424-.432 KOhms, and I've moved them around multiple times.
Moved coils around
Double Triple checked coil wiring to PCM
Whether the injector wires are your way or my current way, the misfires are present, just slightly less at idle my current way
Compression test showed all cylinders 180 to 190 except cyl 1 (200), cylinder 4 took one or two more revolutions to pump up but held pressure at 180 or 185.
Swapped in a new MPFI Spider Injection unit thinking it was fuel injectors, didn't make any noticeable differences ($355 down the drain:()
MMO in the fuel and oil
If I think of more Ill add

Random thoughts of what it could be:

It almost seems like there could be two causes since 3 cylinders are similar and one is way out there. Maybe bad lifter for cyl 4 and something else for the others

Maybe running my wiring "swapped" could have caused issues mechanically

I haven't done a crank relearn for the PCM swap or the 24x cause I never got the code for it. Would that be smart to do if it is misfiring? or could that just mask the problem? I'm not yet all that familiar with what all the info gathered during the relearn is used for. I'll do some looking when I get a chance.

I'm wondering why the Suburban OS didn't register or throw codes for misfires but the Camaro OS does. Can't drive it more than a couple minutes before it throws codes (P0300 and P0304)

Power feels very lacking after exhaust, don't know if that's just because of the exhaust itself or the misfires. Or lack of tuning for it. Bit off topic if its not the misfires though.

Make what you will with this accumulation of thoughts and info, any and all help is absolutely appreciated!

Ok i was talking to a friend. Kinda back on the subject of the fuel trims and injector bank select. Are your O2 sensors wired to the correct bank or are they swapped LH to RH on the opposite banks?

Do you mean at the PCM? I have an extension on one of them but otherwise under the truck they are plugged in correctly. I can recheck at the PCM either tonight or tomorrow morning but it ran fine after the 0411 swap and before the 24x swap. I don't recall removing any pins during the 24x swap, only adding the coils and then swapping the injector wires, and then recently swapping those back.

Checked the O2 wiring at the PCM today, all looks good according to my 0411 swap pinouts

Have you pulled your valve covers and checked things out? lifter ticking would likely indicate some kind of issue there. I had a similar issue on an LT1. I was getting misfires on multiple cylinders but one had a much larger misfire counts then the rest (cylinder 6). I did most of the same things you did trying to diagnose. Swapped injector wiring, coil wiring, tested plugs etc.

I did a compression test and cylinder 6 took a couple rotations to come up to pressure. It did hold pressure once it came up. I ended up pulling the valve cover to check my valve lash and noticed while rotating the engine that one rocker arm on cylinder 6 was not moving. Turns out my lifter retainer broke and a lifter spun in the bore, wiped the cam lobe and destroyed the lifter.

Might be worth checking out.