2007 5.3 help needed

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69-CHVL
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2007 5.3 help needed

Post by 69-CHVL »

I have an 07 Yukon that started running real rough/knocking and triggered the Stabilitack light and check engine light. Code came up stating missfire on #1. Did a compression test and I'm getting 70lbs on that cyl vs 170lbs on the other. This engine does have the AFM which I know is problematic. What's the next troubleshooting step(s)? I will replace the engine if I have to but if a new cam and lifters will do it, that will be obviously alot cheaper. Thanks guys.
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Re: 2007 5.3 help needed

Post by resurrectionjoe »

From a mechanical standpoint I would think a leakdown test would be the next step to test valve job / ring seal.

If you have good leak down numbers then a failed afm lifter could be causing the valve to not open far enough to get good cranking compression numbers.

Maybe then pop a valve cover and see if the intake valves are moving the same amount.

If not you'll probably need this.

https://www.summitracing.com/parts/cmb- ... /overview/
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Re: 2007 5.3 help needed

Post by elmeano »

I'd say drop in a couple lifters if you think that's all that is wrong, if you're changing the cam you might as well swap the engine with a low mileage junkyard deal it would be about the same amount of work.. By popping off a valve cover you should be able to see if the lifters bad based on rocker movement?
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Re: 2007 5.3 help needed

Post by dirtracr5 »

check, check fuel injector, remove valve cover and check rocker movement or for excess lash (stuck afm lifter).

If its a lifter replace ALL afm lifters, and guides.
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Re: 2007 5.3 help needed

Post by jred »

just had the same problem with my 12 silverado check engine light and stab/track light coming on turns out that pack rats got into my truck and ate the wiring harness under the manifold to the vlom valve/lifter/oil/manifold so all 4 cylinder were not working and the truck was in
v4/limp home mode. I have had some repair work that we have done on other trucks that had 1 or 2 cylinders misfiring and it was the lifters and or the roller needle bearing in the lifters that gave out and ruined the camshaft.. time to fix and parts it was easily replace the engine with a new 1 reman one was about 3100.00 not installed repair was about 2300.00 or more
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Re: 2007 5.3 help needed

Post by dfarr67 »

I think on these you don't just throw lifters at them- the head needs to come off.
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Re: 2007 5.3 help needed

Post by jred »

yes thats why so much cost r/r heads /r/r cam liters and gaskets
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Re: 2007 5.3 help needed

Post by 69-CHVL »

Pulled the drivers head and removed the lifters. Pair of lifters on the left are from cyl 1, the one with low compression.

Image

So I'll pull the other head also. My question is though can I replace the lifters with a new set of AFM lifters and just turn the AFM/DOD feature off? Trying to avoid pulling the radiator, cam etc.
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Re: 2007 5.3 help needed

Post by In-Tech »

If the cam is ok, you can replace with ls7 lifters and do the whole AFM delete with the kit above from Summit. Yes, you have to turn off the AFM in the computer if you go that route.
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Re: 2007 5.3 help needed

Post by peejay »

The interesting thing is, the last one I saw with a failed lifter, it passed a compression test just fine.

Pull the valve cover off and start the engine on the other bank, and you could watch the valves working and then after a few cam revolutions, one of the rockers would just stop moving. So the lifter would stay engaged for a few lifts, just enough to do good on a compression test, and then tap out.
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Re: 2007 5.3 help needed

Post by 69-CHVL »

My research has shown than the cam must be replaced if using non-afm lifters, which kinda sucks but whatever. Sure beats having to replace an engine like I was initially thinking!!!!!! (I hope lol).
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Re: 2007 5.3 help needed

Post by A_VAS »

cam does not need replaced no....you can run AFM or non AFM lifters on that cam.

but if you are keeping the cam, and putting new AFM lifters in...might as well keep it active...for better mpg anyway.
too lazy to make power w/o boost
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Re: 2007 5.3 help needed

Post by Kenova »

The lobes for the AFM lifters have a different profile than the lobes for the non-AFM lifters. Two different lobe profiles on the same (AFM) cam.
Will it run with non-AFM lifters on the AFM lobes? Sure it will, but how well?

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Re: 2007 5.3 help needed

Post by A_VAS »

it will run the same as if it had AFM lifters in it, when the AFM is not active
doesn't make sense IMO to do this...since you will have to still turn off the AFM in the computer, change lifter guide trays, and will have a cam that is limiting power

I guess if you were trying to cobble something together with free parts you had laying around, it could make sense.
too lazy to make power w/o boost
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Re: 2007 5.3 help needed

Post by dfarr67 »

I stop by a buddies shop once in awhile, it's amazing what happens to the Hemi DOD when the customer cheaps out on oil changes $$
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