5.3 Colorado spark knock issues are driving me crazy!!! Please Help!

[Colder2012]

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.

[5FDP]

Try 12.0 commanded AFR with 20 degrees of timing, see what happens. Then creep up on the timing if you are allowed too.

I ran 12.0-12.2 on 89 octane with 20-23 degrees of timing on my 2012 LC9 5.3 in my old truck.

Don't forget to disable the cat test in the engine diags exhaust tab too.

[Onomoto]

Any updates on this?

[kevin87turbot]

I know that this is an older thread, but I've had similar trouble with a couple of 5.3L Silverados over the years. Both were 07-08 models. One was a very high mileage engine, with 300k miles. It had audible knock when above 18 degrees timing at WOT. It was around 12.2-12.4 AF ratio, and actually ran pretty strong. I always wondered if the reluctor ring had spun on the crank. I'm certain it had plenty of carbon on the pistons as well. The customer sold the truck before we try cleaning the carbon from it.

Another thing to consider is the type and heat range of spark plug that you're running. If you have an engine that is sensitive to ignition timing, a colder plug can help.