ffr1910

I wanted to place this information somewhere that might help someone in the future. I bought a 2007 Silverado LH6 5.3 with the AFM system about two months ago. It replaced my worn out 1997 Tahoe. Last week, my wife was driving it and it developed a bad miss and sent the computer into a frenzy. We were on the phone at the time and she was in a parking lot within 200yds, my wife know the benefits of stopping when there is a car problem. Computer scan showed #7 cyl misfire. I trouble shot the plug, fine; coil, sparking; injector, squirting. Pulled the driver's valve cover and found the #7 intake rocker arm had about 3/16" of lash in it when it should have none. No problem with the rocker arm nor the pushrod. Turns out the #7 intake lifter is an AFM lifter that disengages to activate the system. It deactivated and never came back online, it stayed in it's compressed state on took the cylinder out of the combustion cycle when all 8 were sposed to be runnin. I ended up replacing all four AFM lifters on the driver's side of the engine and all is back to normal. I hope this information helps someone out in the future-Bill

klingracing

Hello, was wondering if you found the problem that caused the lifter to activate/deactivate. Was the lifter itself the problem or in the solenoid or passage that activates/deactivates. I have the same problem. I am wondering if it is the lifter itself broke or came apart. Thanks

esau999

The OP only has two posts from a few years ago - he likely isn't going to respond. FWIW, I just had all my lifters and cam replaced under warranty in my '13 Avy. It developed a lifter tick with less than 40k on the clock. I don't think lifter failure is an uncommon problem on these engines, either.

warriorpluto

iTrader: (2)

Damn on a 2013? I thought they fixed the problem. I purchased a 06 envoy denali with lh6 and someone had already been into the engine. Has the updated vlom and lifters and cam replaced. I figured it's Ben changed because all gaskets are aftermarket. Valve cover I don't think, does not have the updated valve cover. It's using a quart of oil every thousand miles. I just need it to last me until income tax so I can get a new yukon. Really wished a dumb person never red lighted my 4.2 envoy. Never had to worry about anything with that engine.

chevynut

I just bought a Saab 9-7x (basically a Trailblazer) that had the same issue, a collapsed lifter on cyl #7. Only 88,000 miles and the truck was otherwise flawless, but the shop that the owner took it told him it was the cylinder/piston was bad and it need a new motor for $5000.

I got it for $1500, and knew worst case I would put a motor in it. Well after diagnosing the issue, I am going to delete the DoD and put in a new cam and lifters.

Rare96LT1Formula

iTrader: (32)

There's a reason the DOD Delete kits are selling like hotcakes!

Active Fuel Management/Displacement on Demand setups have been known to collapse lifters (normally more than one) for quite some time now.

Mazzenger

iTrader: (5)

A good friend of mine has an 08 5.3 Z71 with 120K on it. His truck went bonkers. Stabil Trak flipped out and it was missing a little bit.

Dealership and an separate mechanic told him they weren't sure what it was and said it might be a lifter. Said it would cost 4000 grand to fix. But couldn't guarantee that would fix it.

I popped the valve covers and shoved a finger between the rocker and a spring.
One of the AFM lifters were totally compressed.
It even chewed up the tip of the pushrod. Cam was ok, thank the lord.
I replaced them all about a month ago for him to save him a couple grand.
I think those things are junk.