2003 LQ4 runs poorly

[Stepsidelsx]

2-1-16 6.0 (2).hplI have a 2003 LQ4 in a 2500 hd. It throws rich codes and runs very poorly. The truck is stock with no tune on it ever (that I know of). I ran the scanner and found knock for days and everything looked ok, o2 sensors were bouncing and working fine. We changed the plugs and they looked very black. I thought maybe the converter was plugged so I had it changed out with a new gm convertor. no resolve.
SO i pulled a complete file on it and found that the stoich AFR starts off at 14.68 and goes to 9.008 at 100% throttle in a smooth curve. I've never seen this before but I feel as though maybe its my issue. It one of my fleet trucks bought with 25k miles and now has 40k on it. I compared it to other lq4s in the repository and that seems to be the only difference.
Has anybody seen such a thing? I have tuned a few of my "toys" but have not messed with any of my business or fleet trucks. Thanks in advance for any input.
Andrew Ext Cab 6.0 lq4.hptAndrew Ext Cab 6.0 lq4.hpt

[5FDP]

You do know that that table you are talking about is for alcohol content in the fuel right, did you read the description when you highlight the mouse over it??

That table has nothing to do with fuel control at 100% throttle. Your EQ ratio is what you will commaned at 100% throttle.

You should post a scan of what is going on. This seems like a issue with something else that controls air/fuel, like a really dirty MAF sensor or a bad o2 sensor.

[Stepsidelsx]

That's the problem with posting for help. There's always somebody who has to make comments like that one. Yes. I can read. I loaded up the entire vcm. I've replaced all the O2 sensors and cleaned the mass air. That's why I asked.
If you don't want to offer some constructive help, then keep your sarcasm.

[2xLS1]

Don't get your panties in a wad there skippy. Your post indicated you thought the 0-100% indicated TPS%. He was just letting you know that it indicated alcohol % used if it is a Flex Fuel vehicle. The flex fuel switch in your calibration is set to disable since 6.0L trucks were not Flex Fuel. Therefore your calibration will always use the stoich value in the 0% column. Now post a data log with some idle, cruise and WOT data if you want help with a poor running vehicle.

[2xLS1]

And the calibration you posted is from a 06 Silverado 6.0L. But you say the truck is a 03. Did someone change the PCM?

[Stepsidelsx]

I will data log it tomorrow and post. thanks.

[Stepsidelsx]

You know what, it is an 06. My other lq4 is an 03. The 03 runs amazing. The 06 doesn't. Sorry.

[Stepsidelsx]

I added the data log to the original posts

[2xLS1]

For starters you need to be more specific of the problems other than running poorly. Your LT fuel trims are as high as +15%. Closer to setting P0171 and P0174 lean codes, not rich codes. Looks like a typical stock tuned 6.0L truck running in closed loop at WOT because of the PE delays GM programs them with. The O2s will stop switching with proper PE enabling. Yours continue to switch indicating it is still in closed loop. Hard to make good WOT power at 14.7:1 A/F. I would start with a good cleaning of the MAF sensor and a fuel pressure test with a gauge on the fuel rail. Also look for any air leaks downstream of the MAF. All that is to address the + LTFTs. Then if you want better performance tune it. There big improvements you can make on a 6.0L truck if you know how to tune.

[Stepsidelsx]

Thanks for the response. When I say it runs poorly, I mean that when I put a 30 ft trailer on it empty (4000lbs) I cant get the combined unit on the highway because the truck doesn't make enough power to pull that weight to 65 mph for at least a few miles of struggle. I have 5.3 trucks that pull the same size trailer with ease. It throws rich codes on both banks and random misfire codes within a few minutes of reach temperature. I cleaned the mass air with a quality mass air cleaner and even swapped one from another truck with no difference. I would love to tune the truck and get it to run better than the other ones but for now Im more interested in getting it to run correctly. It maintains 58 psi fuel pressure at idle. I don't see a fuel pressure regulator like I have on the 03. At wot is blows black smoke out the exhaust.
As far as tuning goes, Im not an expert by any means, but Im open to suggestions on where to start on it. Torque management?
I really do appreciate your time and effort

[jarrett]

Just looked at my 2006 5.3L tune and it is same way.

[Crashgnx]

Looking at the log I would swear your problem is plugged cats but you have swapped them, have you checked the rest of the exhaust? I know a few years of these trucks had a problem with the mufflers getting plugged by a plate that breaks off internally. Happened to a friends truck. You say its running rich yet the O2 sensors say its not, are either of the manifolds cracked, missing bolts, or leaking somehow before the o2 sensors?