Just purchased a 2007 suburban ltz. The guy I bought it from says he thinks the lifters have been replaced before he bought it. The afm is still enabled, and I want to get rid of it so it doesn't cause me any issues. I know I can either buy the range obdII port disable tool or get a tune. Would there be any harm if the lifters have been replaced in getting a tune? No paperwork to back it up. It has 174,000 miles
Do I need to delete AFM?
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swathdiver
Full Access Member
Not really unless you run it hard and spin high rpms all the time. Do some detective work and see if you can find any service records. The CarFax for mine showed the names of two dealerships which I called and they kindly emailed me all the work done on the truck. Also sent a letter to the previous owner which went unanswered.
After getting a BlackBear tune and turning off AFM the service records revealed that just before I bought it, the entire AFM system was replaced with all the latest parts.
13yukonNJ
TYF Newbie
I don't know why I never thought to do this. I just emailed the service department at the dealership where the previous owner of my truck would take it to be serviced to see if they'll send me their records. I hope they are able to.
EDIT: And to stay on topic, my suggestion would be to leave the vehicle as-is. If it's made it this far without consuming oil I would say just keep being diligent about oil changes.
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iamdub
Full Access Member
If you can find out if the lifters had been replaced, try to find out if it was with the redesigned ones. There's an updated VLOM, too. If it were me and I couldn't confirm either one, I'd at least have it disabled with a tune or Range module. The only way to ensure that it will never be a problem is to remove (delete) it. Disabling it should at least buy you time, though.
swathdiver
Full Access Member
The new and old VLOMs are visually different so one is able to determine if at least that part has been changed on a pre-April 2011 (if memory serves) build.
iamdub
Full Access Member
I just re-read what I wrote. To clarify, what I meant by confirming either one was if the lifters had been replaced and, if so, was it with the redesigned ones.
On that note, I didn't know the VLOM looked externally different. I swear mine has a date of 2014 stamped on it but I didn't know I could tell by it's appearance. Googling!...
swathdiver
Full Access Member
I got ya, such is tough to tell! And there are three designs and the first two are far less reliable then the final Delphi II De Ac lifters which are the same ones used in the Gen V motors.
NathanS
Member
I just went down this same road. If you just bought it, drive it for a while and keep an eye on oil consumption. If it doesn’t burn oil then just leave it. I was burning to much oil for my liking and decided to delete AFM. When I got down to the short block I ended up pulling it and having it rebuilt with a new cam.
trailblazer
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What ups my chances of not having AFM problems? I just picked up a ‘09 with about 93,000 miles and the previous owner used synthetic since when it bought it at 20,000 miles.
Are there any known best practices that seem to prevent AFM-related calamities?
Are there any known best practices that seem to prevent AFM-related calamities?
swathdiver
Full Access Member
It could run trouble free forever or drop dead tonight. Most of us disable the system in the tune to lessen the chance of failure and when a lifter eventually fails, we remove the whole system physically from the engine.
In 2011 the VLOM, lifters and driver's side valve cover were all improved. Under the oil pressure sensor, which is under the intake in the back, is a little filter for the VLOM that gets clogged after time and its worth inspecting or replacing.
Dirty oil is AFMs worst enemy. It is good that your motor has had synthetic oil and hopefully it was frequently changed and not left in there forever.
trailblazer
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I’m going to get an HP Tuners license and kill it then.
The camshaft damage is caused by the plastic retainer for the AFM lifters loosening up over time. this allows the lifters to rotate out of alignment and starve for oil, thus destroying the lifters and associated cam lobes.
Disabling the AFM should not have much impact on the failure happening again because the root cause is the lifters coming out of alignment, not from use of AFM. Only installing the updated lifters and retainers will fix the issue, hopefully permanently.
Disabling the AFM should not have much impact on the failure happening again because the root cause is the lifters coming out of alignment, not from use of AFM. Only installing the updated lifters and retainers will fix the issue, hopefully permanently.
swathdiver
Full Access Member
I thought that was a cause, not the main cause. Collapsed lifters is what I read about most frequently.
It is my understanding that the lifters collapse because the oil port becomes blocked when the lifters are able to rotate slightly in their bore because of the faulty retainer bracket. So the system is still working, but unable to control the lifters that are out of alignment. eventually the lifters fail due to lack of oiling and damage the cam because the rollers on the lifter are out of alignment.
So ultimately disabling AFM will not prevent this damage from happening. only updating the lifters and lifter retainer will.
iamdub
Full Access Member
I believe that if the lifter isn't cycled (pumped up and bled down) all the time so that it operates more like the other 8 regular lifters, then it should live longer just like those regular lifters. So, just disabling AFM should provide a considerable measure of failure prevention. If I were to go into it deep enough to replace the lifters with the updated design, I'm just gonna delete it altogether and be 100% certain that it will never be a factor. I believe that in most cases with the GMT900, AFM may return a 2 MPG improvement on a highway cruise (best case scenario). Figuring for $2 per gallon, deleting AFM and going from 20 MPG to 18 MPG means each mile will cost me one cent more. A rough (and probably rather optimistic) estimate of $2,000 to replace a roached cam and lifters means that it would take 200,000 miles of straight highway driving achieving 20 MPG to break even. I'd rather just not have my engine fail in the first place.
2008yukonxlslt
Member
Hi Chris,
My 08 Yukon has had a single lifter tick on the drivers side for most of the time I have owned it about 9 years but only when cold and during warm-up although it is slowly getting worse. Also has a bit of a manifold exhaust leak. Both go away entirely after engine is warm and if I drive in 3rd around town (no cycling). If I drive in D around town I can hear that one lifter tick a few times as it cycles from 4 to 8 mode. What you said about the rotation makes sense and about the economics of the repair vs delete so I am probably gonna go in and do a delete or replace the lifters and retainers. Would you ever consider just updating the lifters and retainers considering my particular case, again emphasizing that it is just fine once it warms up. I am thinking the cam is still ok and it is only one lifter however I would certainly replace all of them and the retainers. She has 110k miles and is driven pretty lightly. If deleting, would you recommend a kit and what do i have to do to the ECU.
Thx for your time.
Ed
trailblazer
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I’d fix that manifold leak first and see if it’s responsible for the tick. Any exhaust manifold bolts broken off? Inspect them all. I had that issue on my ‘03 2500HD and had to weld nuts onto the broken studs to get them out.
iamdub
Full Access Member
I stand by my reasoning of deleting AFM if I'm tearing the motor down far enough to replace the lifters. The updated lifters may be more reliable, but they are in no way as reliable as the standard lifters that ride in the Gen3 engines for 300,000+ miles. AFM doesn't return enough fuel economy to be worth keeping and it's even less of a difference if you have to go in to the engine again.
The lifters making noise intermittently should be taken as a warning for which you should be grateful. Some people never get any warning- their dash just lights up like a Christmas tree and the engine sputters and dies and they're left on the side of the road. All to save a quarter or two at the pump.
A kit is most convenient. You might can make up a list of all the necessary components and source them from various places and save a little cash. But, from my findings, it's not worth the hassle. I'd order from a reputable supplier such as Texas Speed. There are others, but they always come to mind first.
If you replace your stock cam with it's factory non-AFM version, you won't need any custom PCM programming. You'll just need the AFM disabled in the tune. I had mine disabled a year ago so it'll be just as driveable after I delete AFM as it is now. A local speed shop did the programming for $150. You could do the same to buy you time until you do the delete.
iamdub
Full Access Member
Yes. Deleting AFM requires the lifters to be replaced with regular lifters. The heads have to be removed to access the lifters. If you want/need to delete AFM, don't let a $60 set of head gaskets stop you. An AFM failure will cost you at least ten times that amount.
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