I have been on your site for a couple years now and don’t remember ever seeing this topic. Our issue is we have a 2007 Suburban with a 5.3 AFM (Active fuel management) motor that was burning 1 quart of oil per 600 miles.
We bought the truck with 65k miles on it, now has 75k miles on it. After doing much reading, I found this is a very common problem with 2007 and 2008 models with the 5.3 AFM. My dealer has been more than perfect on getting it “fixed”. They did not request any service docs, instead they just verified the problem by doing a oil consumption test. Once verified, they went straight to replacing all pistons, rebuilt one head, replaced intake, and replaced the valve covers. The truck has since had about 2k miles put on it and all seems well. The oil looks new, before it would be black within 5 miles.
My main concern now is it really fixed? Or is it just patched up for another 30k to 60k miles. (from what I read this is the typical mileage when the problem starts). My dealer told me they had a production run where intakes for non-afm motors were put on the early afm motors in error. This is the first I have heard of this, and cannot find much online about it. The main theory online is that when the AFM shuts off 4 cylinders, they cool, allow small amounts of oil to pass by the rings. Over time this gums the up and they lose their spring tension.
So any insight from you guys or the members would be great. Not sure if I should keep the truck or sell it.
PS: Sorry for any typo’s, did this while at work. Also hopefully this is a good discussion for your piston slap.
Very interesting! I was not aware of this particular problem with the LS Motor…I mean, I knew about LS-series Piston Slap and my love of this motor made me name this column after it…
But I digress. It sounds like the dealer did the right thing and replaced all the offending parts as per GM’s guidelines, so good for them. But, I know, that’s cold comfort to you. And honestly, I know of nothing that can make you feel better.
Except the automotive aftermarket! Hooray for the aftermarket! I suggest you turn off the AFM system and forget about ever running on 4 cylinders. All you need is a computer reflash from just about any GM tune shop, and there are plenty to choose from. Not only does this almost guarantee that AFM will be history, you get a free performance tune for multiple fuel octane levels, no more torque management, quicker transmission action, and far livelier performance.
Send your queries to firstname.lastname@example.org. Spare no details and ask for a speedy resolution if you’re in a hurry.