2012 GMC 6.2L - LIFTER NOISE POST REPLACEMENT

[mbrown_btx]

I drive a 2012 GMC Yukon XL (Denali Version) with the 6.2L engine (with AFM technology still intact) that has 205,000 miles on it. I recently experienced the DOD lifter failure on cylinder 4 (passenger side second valve back) and subsequently replaced all of the lifters on that side only. While I had the head pulled for the lifter replacement, I had it resurfaced and checked for proper operation by a local engine machine shop which I used to get the lifters (instead of buying cheap Chinese lifters from O'Reilly's). After re-assembly of everything there is still a ticking noise (assumed lifter noise) coming from the passenger side. I have checked all rocker arms and push rods for issues and ensured each was re-torqued properly and there was no excess play following re-installation, ticking still exists. During all of these efforts post initial re-assembly I have noticed the fuel pressure after the engine warms up is much lower than normal (less than 20psi while idling), there is an occasional miss, I am experiencing low speed loss of power, and very rough down shifting of the transmission. After reading some posts on this forum I believe I need to replace the oil pressure sensor filter and hopefully that will resolve most of these issues but wanted to post and see if anyone had any other suggestions. I like this truck and want to keep it running as long as possible given it is paid off. Thank you in advance for your reply! 

[swathdiver]

What brand of lifter did the machine shop use?

It is SOP to replace the lifter trays whenever doing this kind of work AND to replace the VLOM as it is the VLOMs solenoids that get out of time and take out the lifters usually.

 

Normal fuel pressure for your truck running from idle to WOT is 43.5 psi.  If she is running 20 psi, see why, and you might have to replace the whole pump assembly.

 

Low fuel pressure can certainly cause drivability issues, fix that first.  Do you have a Tech-2 or something similar for diagnostic testing?

[mbrown_btx]

Thank you for the reply! I did not replace the lifter trays as the engine mechanic I spoke to suggested reusing the old ones rather than replace them with a non-OEM version that would be available. I did not mess at all with the VLOM, I was actually guided to disable the AFM all-together as it seems to cause more issues than it helps.

 

Additionally, I have a basic code reader that will also read some engine parameters but not all of them. I plan to replace the oil pressure sensor filter and maybe the sensor this weekend hoping that is the key issue. If not, where is the pump assembly located in the event that is the next move? 

[newdude]

18 hours ago, mbrown_btx said:

Thank you for the reply! I did not replace the lifter trays as the engine mechanic I spoke to suggested reusing the old ones rather than replace them with a non-OEM version that would be available. I did not mess at all with the VLOM, I was actually guided to disable the AFM all-together as it seems to cause more issues than it helps.

 

Additionally, I have a basic code reader that will also read some engine parameters but not all of them. I plan to replace the oil pressure sensor filter and maybe the sensor this weekend hoping that is the key issue. If not, where is the pump assembly located in the event that is the next move? 

 

 

A bit of ill advice from the engine mechanic.  At 200K you should most definitely have replaced the trays and the VLOM.  The trays are plastic and can be a weak point.  GM has bulletins on the 14-18 motors for AFM lifter failure and no matter the mileage they want those components replaced to eliminate potential re-failure of lifters.  

 

What really should have happened here if they recommended disabling the system would have been to order an AFM delete kit which is new non active lifters, a new cam and a VLOM delete and then have the AFM turned off with HP Tuners.  

[diyer2]

You came to the party late mrbrown. Newdude speaks the right way.

[mbrown_btx]

newdude, thanks! What are your suggestions for moving forward? Do I need to tear it apart again?

[mbrown_btx]

newdude, thanks for the information! What are your suggestions for moving forward? Do I need to tear it apart again and replace the parts that I didn't the first time 

[mbrown_btx]

newdude, thanks for the information! What are your suggestions for moving forward? Do I need to tear it apart again and replace the parts that I didn't the first time around? Not preferred but neither is a large car payment...

[dsr611]

If the mechanic didn't check the cam when he replaced the lifters, I believe I'd find a new mechanic...the failed lifter more than likely scarred one of the cam lobes.  And, ain't but one way to find out...complete tear down and replace all lifters, lifter trays, cam, etc with NON-AFM parts, and tuning AFM out

[richard wysong]

are you having oil pressure or fuel pressure issues? oil pressure usually will not cause drivability issues but is probably the cause of the ticking. possibly the oring on the pick up tube which can be accessed thru the timing cover or drop the oil pan. extensive posts on this problem and the fixes on this forum