Could be helpful to someone out there

[Frasier]

Just sharing the experience with my 2007 Tahoe LTZ 4x4, in hopes that it could save someone some time and heartache.

Headed out on a 1200 mile roadtrip, cruising down the interstate and felt/heard a small knock/pop one time. Thinking I ran over something small and it hit the undercarriage or something like that, I continued on. A couple miles down the road, the dash lit up like a Christmas tree (stabilitrak disabled, service 4wd message, etc), and truck went into "limp home" mode.

Made it to the closest dealership and they found a fouled spark plug. Replaced that, and didn't fix it. Thinking it was a broken valve spring, they started on that. Not the issue either. Ended up being a stuck lifter spring. Took an entire day to tear the left side of the engine down and replace the lifter spring. I went ahead and had them do all 4 while they were in there.

Apparently, with the continuous on/off of the cylinders because of the AFM, this is a fairly common issue.

I have since purchased the Range module to disable the AFM.

 

[harbison]

I purchased the Range AFM Disable but I have a stuck lifter again.

 

[Addicted]

This is a good watchout to be aware of. The qeustion now is, how to prevent it. Harbison, did you fix yourself, or take to a shop? Are the lifters sludged up?

 

[harbison]

This is a good watchout to be aware of. The qeustion now is, how to prevent it. Harbison, did you fix yourself, or take to a shop? Are the lifters sludged up?

Did it myself. The lifters aren't sludged up but man was it stuck! Took a lot of force to get the spring to release. I think the tolerances are too tight on some of these. I replaced all 4 AFM lifters on the left side. The other 3 seemed just fine. Here are some problems I see: 1. Excessive oil consumption. 2. Oil change message usually goes 8-9,000 miles. 3. Tight tolerances cause valve lifter to stick. Others report replacing VLOM. I will keep Range AFM Disabler plugged in and change oil every 3,000 miles.

 

[Addicted]

thanks. Time to search for VLOM.

 

[harbison]

thanks. Time to search for VLOM.

valve lifter oil management. Goes under the intake manifold. GM redesigned it with stronger solenoids and larger oil screens. This is what shuts off 4 cylinders for AFM. Part Number GM #12571609.

 

[Rexter]

yup same thing for me too shop wanted 2k plus to do it.