I just recently bought a silverado that has an LQ9 swap with a 4l80. I'm usually a ford guy but picked the truck up for a decent price. Sadly enough the truck isn't running as well as I'd like and HP tuners shows it's running really lean and throwing knock sensor codes and pulling quite a bit of timing. I checked fuel pressure and at idle it's steady at 58 psi. I know the truck is using the 5.3 PCM- Could this be an issue? It seems to be fuel related. The guy that was using Hp tuners is very knowledgable using that tuning software. Any suggestions would be appreciated. I'm new to engine swapped vehicles- thanks Justin

 

Really need some more details like year of truck and any mods the LQ9 might have. But the 5.3L LM7 tables are different from the 6.0 LQ9. You should try getting a hold Of an LQ9 calibration and copy the tables from that and then tune as needed.

For example the LM7 5.3 fuel tables are bassed on a cylinder volume of 40 and the LQ9 cylinder volume is 45.
I am not familar with HPT but I looked at both of them with my EFI Live

 

^ Yep - and if its a 99 5.3L it may have the 19lb/hr injectors rather than the standard 24Lb/hr, so fuel injector related items will be different.

 

mine did the same thing BEFORE IT WAS TUNED. It was weak...hooked it up and was super lean and timing was at 17*.

Added fuel all over and upped the timing to 28* total and she runs like a raped ape. No more codes, No issues anywhere. 16.5 mpg and loads of power.

It sounds to me that either the tuner didnt have a clue or that ECU is NOT TUNED for the demands of the 6.0L. Good luck man.