AFM lifter fail on my 2018 Yukon Denali

[MrMonte]

Driving home from work my 2018 Yukon Denali with 89K miles was running great. Took off rather quickly from a stop light then shortly after check engine light came on with #7 misfire plus general misfire. Idles a little rough, no ticking that I can hear and exhaust seems to be fuel rich.

Pulled off driver's side valve cover & confirmed #7 has a bad lifter. Pushrod is straight. Gotta work the next 3 nights so plan is to install LS7 lifters & plug the AFM oil lines. All my parts arrived today.

 

[CMoore711]

Sorry to hear about your luck man.

I’m assuming you’re planning to delete the AFM with the LS7 lifters and AFM oil line plugs? Are you sure that’s all that is needed to disable the AFM?

Unless I’m missing something I feel like you’re going to need a few more parts to mechanically delete the AFM.

 

[MrMonte]

I already have the AFM turned off in my tune so the LS7 lifters & plugs should be all I need from what I've read. If I wanted a big cam I would have to delete the VVT but I'm leaving the stock cam in assuming it is still good.

 

[swathdiver]

Pretty sure that on those LT engines you still have to replace the lifter trays and the camshaft or you will continue to get misfires as the AFM lifters are a different length and so are the corresponding lobes on the camshaft. That's how it is on our GEN IVs anyway.

Make absolutely certain you are using genuine parts and not Chicom knockoffs from ebay or Amazon.

 

[swathdiver]

I already have the AFM turned off in my tune so the LS7 lifters & plugs should be all I need from what I've read. If I wanted a big cam I would have to delete the VVT but I'm leaving the stock cam in assuming it is still good.

Head gaskets, head bolts, lifter trays, exhaust manifold gaskets and camshaft too? Flat valley cover? You can get VVT camshafts, Gwatney (GPI) makes some great ones.

 

[CMoore711]

You will definitely need a non-AFM cam. It doesn’t have to be an aftermarket “big” performance cam. In fact, you can use a GM non-AFM cam if you’re wanting to keep it stock.

 

[MrMonte]

Thanks for the inputs. I already have GM LS7 lifters, trays, head bolts & gaskets. Plus the AFM oil plugs.

When I 1st looked at the AFM delete I saw conflicting info about if cam needed to be replaced. The ones that said it did didn't explain why but they were the ones selling the cams.

I understand now the cam lobs are different on the AFM cylinders so I have more shopping to do. I want to keep the VVT which limits cam options.

Again, thanks for the inputs. I'd rather take longer & do right the 1st time.

 

[CMoore711]

@MrMonte Do some research on GM 12664572 you should be able to find one for <$200.

I believe that is a GM OEM Non-AFM cam you can swap into your L86 and retain stock drivability, drivetrain characteristics, and fuel economy.

 

[MobileHomie]

Thanks for the inputs. I already have GM LS7 lifters, trays, head bolts & gaskets. Plus the AFM oil plugs.

When I 1st looked at the AFM delete I saw conflicting info about if cam needed to be replaced. The ones that said it did didn't explain why but they were the ones selling the cams.

I understand now the cam lobs are different on the AFM cylinders so I have more shopping to do. I want to keep the VVT which limits cam options.

Again, thanks for the inputs. I'd rather take longer & do right the 1st time.

Since you have to replace the cam, you may as well do a stage one upgrade...I mean you are in there anyhow.

 

[swathdiver]

Since you have to replace the cam, you may as well do a stage one upgrade...I mean you are in there anyhow.

Yeah, he might as well treat himself to a little extra go go juice for all that effort!

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