2012 Tahoe 5.3 tap/misfire

shafner79 said:

So we dug a little deeper today....with the valve cover off. The #1 rocker is not moving. The hits keep coming. My son crashed our other SUV last week and totalled it.

Any idea on what I need to do to repair it? New motor or is it fixable?

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It's very fixable. I physically deleted the AFM system in my driveway.

@shafner79 That's a common problem with this platform. Moving forward there are a few options in navigating the situation depending on your goals. The proper fix would be to open the top of the motor up and remove the parts of the AFM system and put the motor back together using non AFM parts. It sounds daunting but at this point there should be no critical damage that has been done so getting it back on the road should be very straight forward.

You could attempt to remedy the problem but unsticking the problem part but if the problem happened once, it is bound to happen again.

I have it at in an auto electric shop right now. He is going to try to free it up. He also recommended doing the delete. Which I will be doing as long as the motor is okay.
Hopefully I have some more info tomorrow or the next day on what else he found out.

@shafner79 That sounds like a good plan. You won’t know the extent of the situation until you open the motor but if you can bide time until it’s more convenient I can respect that.

shafner79 said:

So we dug a little deeper today....with the valve cover off. The #1 rocker is not moving. The hits keep coming. My son crashed our other SUV last week and totalled it.

Any idea on what I need to do to repair it? New motor or is it fixable?

Click to expand...

Shit, man! I hope your son is okay.

Geotrash said:

Shit, man! I hope your son is okay.

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Thanks! Yes he and his friend were fine.

I found a shop that will do an AFM delete and replace all the parts with non AFM parts. He's going to do the heads and put head gaskets on it as well as the lifters and cam. Then I have a friend with the HP tuner who will reprogram it for me. Looks like it's going to be over $4,000.

shafner79 said:

I found a shop that will do an AFM delete and replace all the parts with non AFM parts. He's going to do the heads and put head gaskets on it as well as the lifters and cam. Then I have a friend with the HP tuner who will reprogram it for me. Looks like it's going to be over $4,000.

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That's a fair price but keep in mind that you'll need to have it tuned before it's started for the first time without the AFM components. You may want to have him grab the current tune files off it now before it goes under the knife, so he can make the changes and flash the ECU while it's still in the shop.

Once they stick with AFM enabled you can free it up but it will stick again unless you disable the AFM system before you run it again after freeing up the lifter. You have to pull off the intake manifold as part of freeing it up. I have done a couple engines with your exact issue, I used the tool to pop it free or unlock the lifter. Then I deleted the AFM system so it will not be activated again which will keep it functioning normally as an 8 cylinder. This can be fixed for reasonable money. The correct fix is to remove both cylinder heads and install all new lifters and while the heads are off do a valve job. It is up to you how you fix it. Most shops are afraid to remove the heads so they all tell you to get a new engine. There is a shop in Texas that supplies the tool and parts to release the lifter and delete the AFM. You can find it on Youtube. After this is done the AFM needs to be turned off inside your computer. There are usually local guys that will do that for $100. Inside the GM computer there is an On Off switch for AFM, it asks, does this vehicle have AFM, and they change the answer to No. From that point forward AFM is no longer active and the car runs perfectly as a normal 8 cylinder engine. Converting the AFM VLOM to non AFM is simple but for $50 you can buy a non AFM manifold off amazon and use it. Shops will not do this type work but for a guy that works in his garage it is an easy fix compared to pulling the heads off.

Video showing how to release the stuck lifter.