AFM-active fuel management leads to failed lifters and engine
 

Anyone contemplating a 2007 or newer Chevrolet with the 5.3l V8 needs to Google any forums relating to their AFM "active fuel management" system.
You will learn immediately of serious and very costly engine problems. MANY stories on the web are typical of my own experience. I purchased a new 2007
Suburban and despite maintaining it meticulously failures consisted of, transmission replaced 32k, overheated differential 53k, several fuel emission control problems,
and the main point of this reply a failed engine at 72k. Seems Chevy decided to incorporate a fuel saving system which shuts off fuel (injection) to 4 of the cylinders
while under light loads to save fuel. The engine is designed to also close off those particular cylinders by collapsing the valve lifters (electrically) so that these same cylinders in
effect act as an air spring. Short version is your running on 4 cylinders. Great idea EXCEPT the non firing cylinders have no combustion pressure to force the piston rings out aginst
the cylinder wall and seal as they are designed. Thus oil is allowed to pass to the combustion (Top) side of the piston causing a huge oil consumption problem. Forums are riddled
with this FIRST complaint. My 2007 was consuming 3 qts between oil changes at 5k. This began at about 25k miles and steadily increased.
A more serious problem is when the valve lifters are constantly shifting (solid/collapsing) they are pron to failure. As many here know a failed valve train is a SERIOUS casualty .
My Suburban suddenly lost one cylinder at 58k. I thought it was a bad ignition coil pack but had to take it to a GM shop. They said it was a "stuck lifter". This really didn't much
sense to me but i paid and moved on. At 72k same thing #7 cylinder dead...Went back to dealer and was informed "collapsed lifter". Next they said that to know what really is the cause the cylinder head would need to come off (which is true with the LS engine), cost $1800. They went on to say that it would be best to replace all the lifters while they had it apart, (which is also true) another $1800. They acted as if this was a new event for them. I told them "hold on" I need to do some investigating. Sure enough I went on line to educate myself and the first Chevrolet forum I looked at described my EXACT SAME PROBLEM followed by MANY others. Why didn't the GM dealer just be upfront with me? SECOND complaint. So I was faced with ~$4000 repair bill OR (as I had to work out) I could replace the engine with a rebuilt long block for $6400. This was on my 7 year old vehicle with 72k miles! By the way the local customer rep for GM could only offer a "customer loyalty discount" of $2000 off a new $50k Suburban...! So my next step was to call GM and see if they could help...HA GOOD LUCK on that. I was hoping for a little HELP towards the purchase of the long block, even a $1000 bucks would have been something. Here's what you can expect, first GM makes you feel like they're with you by "filing a claim" next after 4 or 5 weeks of "we'll look into it," they send your file to the "lead claims rep" (aka. the cubicle next door). I dealt with this run around for 3 months and the dealership didn't seem to mind my Suburban taking up their stall space (maybe they've seen this before) (again why didn't they just be up front and spare me the trouble). BOTTOM LINE, I paid the $6400 for the rebuilt long block. I feel why repair an engine and not fix the inherent problem? The newer engine has had some "redesign to address this problem" thus essentially admitting to the problem. I really try to give "American made" my business, but I will no longer EVEN CONSIDER a GM product. By the way later on I see that this vehicle was made in Mexico, What the....Maybe it's true what the say about NAFTA. Anyway I hope this will be some help to others as others have helped me with internet entries.
MJA