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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[MrMonte]

@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.

I ordered the GM 12664572 cam. This is the same cam in the Escalade V. This cam will go nicely with the future supercharger install.

 

[MrMonte]

Only spent 2hrs on the Yukon today. Was determined to get that intake cover off then bagged/labeled all bolts removed so far then sprayed exhausted bolts since they tend to break. Removed all pushrods & rocker arms which all look good.


That wiring bundle attached to the back of the intake cover was a pain. I ended up removing the alternator so I could remove the intake leaving the intake cover still attached by 4 connectors in the back which I could now reach.

 

[MrMonte]

My son bought a 1999 Suburban for $1,000 that had 2 month old tires & tags that cost over $1,000. Cosmetically it needed some help but runs & drives great. My grandson wanted to help so yesterday he help me wet sand the tired paint with 1000 grit, buff then polish. The water spots must of been from 1999 because even claybaring wouldn't touch them. Ended up wet sanding the glass with 2000 grit. Also sanded/cleared the headlight to get them clear again.

As for my Yukon, hoping to get my cam this week I checked the status & it was cancelled due to backorder even though when I ordered they said it was in stock. They didn't let me know it was cancelled. I ordered a Scoggin Dickey cam which spec wise looks to be better than the ZR1 cam I had order but was $100 more. I did remove the exhaust bolts from the Yukon today so some progress. I have to work 50hrs between now & Wed morning so not much happening on the Yukon for a few days.

 

[MrMonte]

Still waiting on my cam & a harmonic balancer puller so progress has been slow. Pulled the water pump & the head that had the lifter failure. All rollers on the lifters are good as well as the cam lobes. The bad lifter separated. Harmonic balancer bolt has been removed with the help of a 5 second blast of heat & a HD impact

 

[Ibustbravo]

You can rent a harmonic balance puller from advance and auto zone..

Someone correct me if I'm wrong but I don't think you can get the cam out of there without removing the oil pan and at last the engine mounts and likely the front axle & steering. You'll see once you get the front cover off. The oil pump is half in the pan and half out of it. And the distance between the crank and the cam is too short to get the chain out of there.

 

[MrMonte]

You can rent a harmonic balance puller from advance and auto zone..

Someone correct me if I'm wrong but I don't think you can get the cam out of there without removing the oil pan and at last the engine mounts and likely the front axle & steering. You'll see once you get the front cover off. The oil pump is half in the pan and half out of it. And the distance between the crank and the cam is too short to get the chain out of there.

Yes you can leave the oil pan alone & that is my plan. I watched 2 videos where the oil pan was left alone & cam replaced. Tricky but doable. I'm up for a challenge.
As for the puller my 1973 Camaro, 2014 SS Sedan & 2018 Yukon are all 6.2L LS/LT powered which need a special puller so gives me a good excuse to get another tool.

 

[Ibustbravo]

Yes you can leave the oil pan alone & that is my plan. I watched 2 videos where the oil pan was left alone & cam replaced. Tricky but doable. I'm up for a challenge.
As for the puller my 1973 Camaro, 2014 SS Sedan & 2018 Yukon are all 6.2L LS/LT powered which need a special puller so gives me a good excuse to get another tool.

I just did a cam swap with the engine on a stand. I think I watched that same video. I couldn't get it that f'in cam sprocket to clear. I gave up too easy.

When you're looking at pulling the engine you get a lot more determined. heheh..

 

[MrMonte]

I just did a cam swap with the engine on a stand. I think I watched that same video. I couldn't get it that f'in cam sprocket to clear. I gave up too easy.

When you're looking at pulling the engine you get a lot more determined. heheh..

I've rebuilt & did cam swaps on many engine over the last 50 years but this is my 1st LS/LT experience so I watched many videos. Key learnings: leave the injectors attached to the head if a head rebuild isn't being done, those 2 flex belts can be removed easily without cutting, it's possible to remove cam without dropping pan or loosing oil pump & if you do loosing or remove oil pump install those oil pump alignment brackets.

 

[Ibustbravo]

I've rebuilt & did cam swaps on many engine over the last 50 years but this is my 1st LS/LT experience so I watched many videos. Key learnings: leave the injectors attached to the head if a head rebuild isn't being done, those 2 flex belts can be removed easily without cutting, it's possible to remove cam without dropping pan or loosing oil pump & if you do loosing or remove oil pump install those oil pump alignment brackets.

Yea, this was my 1st LT rodeo as well. I had to pull and replace the engine because a rod went through the block.

Let me know how it goes. I read you can also clearance the pump with a couple twenty thousands feeler gauges. I used the brackets too.

 

[MrMonte]

Less than 1 minute after the harmonic balancer puller arrived I had the harmonic balancer off.
Cleaned the carbon off the pistons. Tried for a few minutes to remove the timing chain without loosening the oil pump like the video I watched but didn't get anywhere. Haven't given up but I did order the oil pump alignment fixtures just in case. AFM delete plugs are in.

Work owns me for 15hrs/day until Thursday so hoping to get my Yukon back on the road next week. Got a big road trip in 2 weeks so no pressure. LOL