FleXJ

So my wife drives a 2010 Yukon xl, 5.3. The last couple weeks it’s been intermittently misfiring on cylinder 1, ticking very bad and running very rough, but it comes and goes. I’ve changed plugs, wires, oil pressure sensor, cleaned mad, move coil pack 1 to cylinder 2. Keeps miss firing on 1.
So I pulled the rocker cover and both rocker arms on cylinder 1, at top dead centre there’s about 1/8” difference between the 2 push rods…… does this confirm collapsed lifter before I tear it apart?

FleXJ

Tyler Dietzenbach

iTrader: (5)

The only way to know for 100% certainty is to yank the heads and look. These things collapse lifters all the time.. Reason why I've stayed away from AFM motors over recent years.

FleXJ

So I went ahead and pulled the driver side head, lifters look the same but you can tell cylinder 1 is not running the same

69-chvl

iTrader: (11)

Did you do a compression test before you took it apart?

FleXJ

Yes and it was good but the problem is intermittent, so I never got to test when it was acting up, I’m thinking of changing both number 1 lifters, and the whole vlom….

Tyler Dietzenbach

iTrader: (5)

I'm about 99.9% sure that a lifter can appear completely normal when not under load, but the second it's actually under load, it can collapse. They lose their ability to hold.

FleXJ

I’m hoping your right…. Either that or it was the vlom the whole time, but she had a broken exhaust stud on #7 so at least I can fix that

SAPPER

iTrader: (10)

When an AFM lifter collapses, it stays collapsed.. What does the plug look like? #1 & 7 will oil foul real bad.
Otherwise according to your pic of the pushrod being lower, was the cam lobes both on the heels of the lobes? basically TDC on that cylinder.
If you do do lifters, replace the VLOM, that is usually the primary culprit of a lifter failing.
Also, from the looks of the lifters, you really need to run a better oil. That Valvoline **** ain't cutting it.
But you need to check the cam lobes and/or a roller on the lifters for any type of damage. One little nick will make it misfire.
After you fix it, do whatever you need to to disable the AFM, the lifters won't activate which you have a 99.9% chance a lifter wont fail and it will probably not burn oil anymore. With AFM on, I see the usual 1 to 2 qts of oil burnt every 1,000 miles.
I work at a dealer, have done more of these than I can count and customers pay me on the side to disable it via HPTuners. I tuned over 25 Police cars (Caprice) and none ever had a lifter failure.

FleXJ

Ya she gets her oil changed t those drive through cheapy places, it also has 340 000 km on it. Can the Afm be disabled with changing any mechanical parts?

wannafbody

iTrader: (2)

I've had AFM lifters fail on both sides. The lifters I've seen at my mechanic's shop have always had the spring compressed.

FleXJ

Ya I’m actually thinking it might Have been the vlom the whole time.

69-chvl

iTrader: (11)

When I lost a afm lifter on my 07 5.3 I didnt think I was even going to make it home, but did just barely. Lifter was collapsed. Replaced all lifters with regular jobs, new 5.3 non-afm cam, and sent the ECM out to have the afm disabled. 40k miles later still running perfect.

SAPPER

iTrader: (10)

Yes, it can be done with a custom tune or now they even sell a plug in deal that goes in your DLC and disables it as long as its plugged in. Google it.
I've backed off from heavy work due to health issues here at work. But I was doing 2 to 5 lifter jobs a week at one point. Which I didn't mind, kept me from rebuilding these POS 6L80s.

FleXJ

So further inspection, the roller on the Afm intake lifter is pitted but the can love looks ok, not sure what this means

FleXJ

LilJayV10

iTrader: (39)

It means you need to do a DOD delete before you tear something up that takes the engine out.

FleXJ

Ya that’s the plan, from the research I’ve done…. I can leave the high volume pump and oil relief valve in place…. Change cam, lifters and tune it…

FleXJ

Another question, I have my old 4.8 gen 3 cam from my c10, I can use that correct?