Please Help! Knock Retard...False, Real, Figment of Imagination?

[matts]

First off I'm still a newbie. I read a LOT and think I have a somewhat decent understanding of what's going on. I've searched and read and banged my head against the wall and I still can't get this figured out. I really believe this is false knock. Nothing seems to touch it.

The vehicle is a 2013 Tahoe with 5.3. The only thing it has done to it is a cold air intake tube (stock style paper filter, not oil soaked) and colder spark plugs (NGK TR5). It shouldn't be this difficult lol. I've looked at other posted tunes from similar vehicles that are much more aggressive in the timing dept than this thing is and I CONSTANTLY get knock retard showing up on the scan.

I've tried going richer via VVE, MAF, and both. I've tried going leaner VVE, MAF, and both. I've tried going richer and leaner in what seems to be the problem areas. I've tried going back to stock MAF and VVE. I've tried 87, 89, 93 (with and w/o ethanol) and nothing seems to help. I changed from the factory plugs and wires (with 60K miles on them) to brand new factory wires and TR5 plugs....still getting retard showing up. I've started over from scratch a few times. I've resorted to tinkering with the knock sensors thinking i'll get them just to the point they leave me alone and will still pick up actual knock (I haven't went wild with this approach, about 10% max). I've even tried taking both high and low tables down so low that I'm getting passed by the kids in the neighborhood on their skateboards and it still seems to pull about the same knock retard out no matter what the numbers.

I've played with most tables that seems like it would have an affect on the outcome. There is no audible knock. It seems to do it most often (95%?) under enough load that the intake is making some noise (uphill, moderate throttle, etc). I don't remember if i've went back to stock intake tube and tried that. I haven't replaced the knock sensors yet, but they look like they're in good shape (no visible damage).

This particular scan is nothing specific. Just a drive down the highway going to run an errand. I can do 100 scans and they'll all be pretty similar to this. The tune I'm attaching is what was in the truck at the time, and the stock file for comparison. The fuel trims aren't the prettiest, but at this point it doesn't seem to make any difference . Is there something simple I'm missing oh guru's of the ECM? I'm all ears whether it's something simple and stupid or something complicated. I'm willing to listen! If there's something else I've screwed up on, or need critiquing I'm all ears as well. Thanks in advance.

Oh. I've used a wideband and factory 02 sensors and neither one seemed to make a noticeable difference in this issue.

[5FDP]

Under moderate to heavy throttle how close was the commanded afr to the actual AFR when you used the wideband?

Seems a bit strange that even with 93 octane and okay timing that is showing as much knock as it does. 20-25 is a good spot to be in a truck through for a commanded timing.

[matts]

I don?t remember exact numbers, but best memory serves me i had it within .10 AFR pretty much across the board. I?ll put that file and wideband back in this weekend if i get a chance.

I also looked all over that thing for any spots that looked like it had been hitting each other and maybe the sensors were picking that up.