2013 Yukon 6.2 with p0304 code

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mountie

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I just replaced a broken valve spring on my 2013 Denali. Had it towed to a local shop that said they did diagnostics on it and gave me a quote for $5500 to replace the lifters. Told him I’d do it myself and had him tow it to my house. Spent 45 minutes removing the valve covers and found a broken valve spring. Got lucky that there was no damage to the valve or piston and got it back up and running.View attachment 440732
That is an 'ouch'....... I hope my '05 5.3 doesn't do that..... Or is it on your newer engines?
 
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Budzy24

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Update: So i pulled the vlom and tried the plug from cpr to block oil to the lifter. While i had the intake off, jumped the starter relay, and the valve would work first 5-6 strokes and then quit moving. I put in the plug and put it back together and still same thing, misfire in 4. I havent messed with it since, had a vacation last week.

I am now researching a delete, assuming i have a bad lifter. Trying to decide if i want to do a stage 1 while i have it tore apart or go back stock.
 

j91z28d1

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Update: So i pulled the vlom and tried the plug from cpr to block oil to the lifter. While i had the intake off, jumped the starter relay, and the valve would work first 5-6 strokes and then quit moving. I put in the plug and put it back together and still same thing, misfire in 4. I havent messed with it since, had a vacation last week.

I am now researching a delete, assuming i have a bad lifter. Trying to decide if i want to do a stage 1 while i have it tore apart or go back stock.


did you happen to clip the gasket around the holes leading down to the lifters? that vents any oil pressure thst might build up in there and release the lifter.
 
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Budzy24

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did you happen to clip the gasket around the holes leading down to the lifters? that vents any oil pressure thst might build up in there and release the lifter.
I did not clip the gasket, if I do and oil does get in there below the vlom is it able to drain back to the oil pan? I blocked oil to the vlom because I feel like after it builds oil pressure is when the lifter collapses but the vlom plug didn’t work. Would have bet money it was a solenoid leaking by to the lifter.
 

j91z28d1

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I did not clip the gasket, if I do and oil does get in there below the vlom is it able to drain back to the oil pan? I blocked oil to the vlom because I feel like after it builds oil pressure is when the lifter collapses but the vlom plug didn’t work. Would have bet money it was a solenoid leaking by to the lifter.


yeah, he's got a video showing clipping the gasket. I did mine, so as I understand it when the vlom solenoids are closed and not supplying oil down the hole to release the lifter, they are vented to allow oil that comes from around the lifter bore to not build up pressure. if that vent becomes plugged up somehow, and the lifter bores get worn. the oil pressure can build up.

no clue if that fixes anything. maybe your lifter lock pins have become worn or something. but thst the theory anyways.
 
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Budzy24

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yeah, he's got a video showing clipping the gasket. I did mine, so as I understand it when the vlom solenoids are closed and not supplying oil down the hole to release the lifter, they are vented to allow oil that comes from around the lifter bore to not build up pressure. if that vent becomes plugged up somehow, and the lifter bores get worn. the oil pressure can build up.

no clue if that fixes anything. maybe your lifter lock pins have become worn or something. but thst the theory anyways.
Makes sense to me what you’re saying and what he’s showing. I may give this a shot before buying anything else. Why do the blank valley covers have orings to seal the towers and some suggest plugging as well.
 

j91z28d1

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Makes sense to me what you’re saying and what he’s showing. I may give this a shot before buying anything else. Why do the blank valley covers have orings to seal the towers and some suggest plugging as well.

those are for when you replace the afm style lifters with standard lifters. at that point there's no need to vent oil.



I did mine as preventive maintenance. got it at 135k and turned it off in the tune with hptuners on the drive home and did the pressure block and gasket clips as soon as I had time. at 162k now and fingers crossed it makes 300k. I have the hybrid yukon version and there's no delete kit for it. it's a special grind late intake valve closing with higher compression pistons to compensate. I don't believe I can just slide a standard grind cam in it and it run correctly. there's a few posts about guys doing it, but when I ask if it worked no one seems to reply. so I'm taking it as a no. hptuners isn't well defined for the hybrid ecm. has very limited adjustments. I don't believe I have access to what I need to tune for a standard cam.

sadly I don't even know if gm sells this cam anymore. so I figured anything I can do to make it last was worth the small mpg loss. I did consider replacing the lifters and vlom with oem ones but pulling the heads over it seems like a hassle I would like to avoid as long as possible.
 

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