The 2007-2011 Silverado's with the 5.3 are terrible, plain and simple. Tons of build quality issues, and GM definitely did not have the AFM figured out yet. If your 2007 Silverado can't tow a light load on 89 grade octane without knocking, something is wrong with it. A custom tune could probably correct it and disable the AFM as well, but I agree that you should not have fix poor factory engineering out of your own pocket. For a reliable tow rig, a 2500HD with the 6.0 would have been a much better (albeit thirsty) choice.SMITTY wrote: ↑Thu. Feb. 09, 2023 9:25 pmIn theory they adjust, but we all know reality is much different.
Case in point, my '07 Silverado with the LMG 5.3 - also flex fuel. Knocked like hell on 87 when at full bore or towing, right from the day I drove it off the lot. I made it knock on the test drive! The computer just couldn't pull enough timing out of it. When I started towing more frequently I just bit the bullet and kept her full of 93. Only thing that makes it go away.
One time I was being a cheapskate and tried 89. Had to haul a car up to ME that week. I couldn't go over 50 MPH on hills, or else I'd have scattered the engine all over the highway! You should've heard the violence happening inside all 8. Makes me cringe just thinking about it. I couldn't give it any more than 1/4 pedal!
Back in the 80's when fuel injection was coming out mechanics were saying "it won't last, you will never be able to fix it, etc". Yet here we are talking about how reliable some of those vehicles turned out to be. Sure there were some that were junk - that was also true of carbureted vehicles.
Same for us. We recently traded our 2016 Expedition with the 3.5 Ecoboost and it was still running like new after 130K miles on 87 octane and Motorcraft oil changes every 5-6k miles. We replaced it with a 2020 Expedition, which has the 2nd Gen. 3.5 Ecoboost. It too has excellent performance on 87 octane gasoline.