Hi guys, I am normally over at corvetteforum.com working on various things on my C4 vettes.

I have a family of 4 and a 5th on the way. I came from a family of 5 and I grew up with my mom hauling us around in a suburban. We are buying a sub within the next couple weeks and i have been researching the afm related issues with the gen 11 subs. holy crap seems like this a huge problem or am i offbase? I feel like if i buy one these i have a 75% chance to have issues. the alternative is to back up and buy a generation 10, which i am fine doing.

i have a set price i want to stay under and it means i could get a high mileage gen 11, or a generaton 10. i am fine wrenching on anything other than inside the engine or tranny. so this is why i am posting to get your guys honest take (from owners of the 5.3 with afm) on is this issue really rampant?

my understanding of the afm related issues is the following:
- creates a situation where moving parts in cylinder are starved of oil when they are not being fired in the v4 mode
- overheating in said cylinders may cause the ring gaps to become aligned, causing extreme loss of pressure and blowby, engine begins to consume oil?

-is that a correct understanding of the afm issues?

- is a a high mileage gen 11 sub with the 5.3 a bad idea? if it has already been serviced for the afm related issues and then blear beared to turn off the afm would this be acceptable? If it is a high mileage afm 5.3 and has never had any issues, should i expect them?

- do a cylinder leakdown test to see current condition of cylinders is this a must for these cars?


i absolutely love the look of the gen 11's of all the previous generations. however that takes a back seat so to speak when it comes to a family mover. i will buy a generation 10 if this 5.3 afm issue is really as bad and rampant as it seems from doing owner review research on the web.

any comments you guys have will be greatly appreciated and soon i will own a sub be it a gen 10 or 11.

regards and merry christmas, VikingTrad3r

 

I've had no (engine) or vehicle mechanical issues w/my 2009 LTZ.

I have had various other issues which have made me question my sanity and the price tag of this vehicle when I bought it new.

If you are searching, the 09 added a 6 speed auto (vs 4) and bluetooth.

I suggest looking for a 2010, or if budget allows, anything under the 3 year, 36,000 mile mark.

That way anything you find will be covered.

My next vehicle will be purchased this way... as was my last one (my jeep). (1 year old, 12k on the clock, and full factory warranty, for 8k off price new).

As for AFM, it hasn't been an issue in my 09. The only time I had a near issue was after a summer of towing a 6,000 lb trailer, and ended up with low oil.

I've never checked the oil level... (why should I?) I've only ever changed it w/the reader got to 15% life remaining.

So, that is, maybe my own fault.

Other than that, no AFM issues.

Also, no one posts "hey my vehicle is working great" online... so your perception is accurate, but based on a skewed data set...

 

I will second that... I have a 2007 with the 5.3L AFM and have now over 100k miles and have no mechanical issues what so ever, I do check my oil regularly but have no consumption issues.
Its seems the AFM failure and oil consumption go hand in hand...

 

that is nice to hear two people with trouble free engines. keep them coming! i want to buy a gen 11 and maybe with enough "no trouble here" stories i will. pretty gunshy right now though

 

I guess I live under a rock - I have no idea what platform are the 10th and 11th generations. I know GMT800, GMT900, GMT400, etc. I assume the GMT900 is 11th gen?

You can avoid AFM altogether by:

1) Getting a GMT800 - '06 or older
2) Getting a 3/4-ton GMT900 - rare, kind of hard to find, but absolutely bulletproof
3) Getting a GMT900 Denali - 6.2L engine with no AFM.

It appears most of the AFM issues are in the older GMT900 trucks. 2010 and newer don't seem to have as many issues (or maybe the overall fleet hasn't racked up enough miles?).

I'll be buying an 07-09 for my daughter in the next 3-6 months. I'm looking at Sierra Denalis, Yukon XL Denalis, the Escalade EXT or another 3/4 ton Burb. None of them have the 5.3 motor.

 

How appropriate that I finally sign up for the forum (after lurking for about 9 months) and this is the first post I see. If I may hijack the OP's thread for a bit... (And further apologies for probably posting something that's been discussed before.)

My 07 with the 5.3 AFM engine started making weird noises just as my wife got home with it last night. She said there was a loud pop and flapping sound and that everything stopped working. Fan belt, I thought. No big deal. Nope. Fan belt is still in place. I started it this morning and the Stabilitrack waring is on, the traction control light is on and the check engine light came on for just a bit then turned off. The engine is making a clunking sound - faint - and it gets worse as you rev it. Obviously.

I'm not sure if it's AFM related or not. I haven't had time to look. We just had the oil changed and no warning light about low oil level. And I haven't really checked the oil level, either, though. My bad.

Any of you guys know what might be the problem? I'm checking the oil when I get home from work because I thought about doing that too late this morning - I'd already stared the engine.

By the way... hello everyone. Glad to have finally signed up.

 

Welcome to the forum
for sure check the oil level, might also check the plugs, look for excessive fouling on plugs 1 and 7 as they seem to be bigger indicators...
Now this not to say that is the problem but those plugs fouling out more so then than 3 and 5 with the AFM.
You may want to check compression on those cylinders also that will give a much clearer picture if one of the AFM lifters has failed...

 

I have an 08 Sub 1500, 5.3 with AFM and the 4sp tranny. Have 105K miles and had no issues at all with oil consumption. I chg the oil regularly @4-5K with dino oil.
Now there have been a few other issues with the truck but overall I'd buy again.

I'd probably go to the 2500 next time tho.

 

I should have posted for reference. I'm around 80,000 miles in.

Or $14,500 in gas.

 

Thanks!

The oil was down to about the 2nd hole on the dipstick. (It's never used that much oil since we bought it in April of last year... 110K on the clock now.) I haven't checked the plugs yet... don't have the tools, I'm sad to say. Anyway, I talked to my mechanic friend and he's pretty sure it's the AFM. I'm probably going to swap engines (ugh) for a non-AFM unit.

Now the big question... dealership or local garage? LOL