I am having an issue with spark knock on my truck, any insight will be greatly appreciated, I have been fighting this issue for too long now.
Truck is a factory 09 Colorado with a 5.3. Non DOD / Non VVT. Mods include:
-Cold air intake
-Electric fans
-Cat Delete
-3" exhaust
The truck has an audible spark knock at WOT. Advance is not super aggressive, I believe it is 25 degrees at peak advance. I have tuned multiple LS engines with peak advance at 27-28* with no issues. I tried lowering the whole high octane table by 4 degrees and was still getting an audible knock at WOT. I figured the cats may have been partially clogged causing high cylinder temperatures, I had them removed, no change. AFR is 12.5-13.0 WOT. The knock is real, it is not false knock. I can put maximum advance at 17* and get no knock retard but the truck is a complete turd at 17*. The truck has not had 87 octane fuel in it since i have owned it. I did a seafoam treatment on the engine recently hoping to clear out any carbon build up.
Would someone mind looking over my tune and scan and possibly provide some advice?? I am lost. I guess my only option going forward, if there is not an issue with the tune, is to convert the truck to E85.
Thanks in advance.