AFM/DOD issues

[TxMarine]

I am new to this group so please bear with me as I know this is an old thread. I have read a lot of the comments on this specific thread as I am trying to figure out what is my problem on my 2008 Yukon XL. Hopefully someone on here might be able to shed some light as I havent seen anyone post similar symptoms. When slowing down or letting off on accelerator, I start feeling a shudder. As someone mentioned, you shouldnt feel it when it goes into V4 mode but I feel it very well on this vehicle. It will do this around 20 to 35 mph. Once the vehicle slows almost to a stop, it goes back to V8 mode. Or, if just slowing down around those speeds, then accelerate, it goes back to V8 mode. Oil consumption is as most of you mention. I probably have to add 1qt every 3 to 4 weeks. When I purchased the vehicle used in 2012, it ran fine. It does not do it all the time though. Mileage is about 150000, give or take a few hundred miles. I also have a 2008 Silverado with the same engine and it runs fine. Almost perfect! Just trying to find a solution that will go easy in my wallet! Thanks in advance!

 

[Mooseman]

The post has been moved to its own thread. It was originally in the
How to disable AFM/DOD at no cost thread.

I had the same issues. I could feel feel it kick in and went through oil fairly quickly. I have since both permanently disabled it via a tune and also changed all the hardware to non-DOD valvetrain. This is a troublesome system, at least for the first few years. Try disabling it by disconnecting the vacuum sensor on the brake booster and see what happens. Also compare with the fuel consumption (hard calculated MPG, not what the DIC says or your guess-o-meter).

 

[Sparky]

I tuned mine out with a Diablo handheld tuner on my 07 Silverado. Got rid of the slight shudder and virtually ended oil usage (which started very suddenly).

You can get a Range AFM disable device that just plugs into the OBDII port. It is cheaper than a tuner but I opted for the tuner so I could also adjust for tire sizes etc.

 

[northcreek]

I use the Range disable on mine and it works great. I don't believe that your Silverado uses AFM, I know that my son's 09 does not but, he has the Vortec 5300 LMG (VIN code "0") engine which is the flex fuel version of the LY5...Mike

 

[Sparky]

The 5.3 was the only one with AFM from 07.5-13. The 4.3 V6, and the 4.8, 6.0, and 6.2 V8s do not.

 

[TxMarine]

The post has been moved to its own thread. It was originally in the
How to disable AFM/DOD at no cost thread.

I had the same issues. I could feel feel it kick in and went through oil fairly quickly. I have since both permanently disabled it via a tune and also changed all the hardware to non-DOD valvetrain. This is a troublesome system, at least for the first few years. Try disabling it by disconnecting the vacuum sensor on the brake booster and see what happens. Also compare with the fuel consumption (hard calculated MPG, not what the DIC says or your guess-o-meter).

I will try that. At least until I decide whether to get a tune or use the plug in. Thanks!

I use the Range disable on mine and it works great. I don't believe that your Silverado uses AFM, I know that my son's 08 does not but, he could have the 4.8.

No...I know my Silverado. Plus, its kinda hard not to notice the DIC going from V8 to V4 mode.

Moderator edit: Please use the Multi-quote feature instead of multi-posting. Posts have been merged.

 

[Mike534x]

I don't believe I ever had a shudder whenever my TB would enter/exit V4 Mode, it did have the infamous "surging" feeling whenever coasting down the main road/level highway but that was it and the "exhaust chatter" when coasting. Oddly enough it stopped surging after it had the even number lifters replaced when #4 failed back in May. Not sure if it had to do with the newer style lifters (same ones they use in '13+) but it definitely still ate 2 1/2 to 3 quarts of oil between oil changes.

Since mine is totaled out, and the insurance company refused to give me coverage even if I bought it back/rebuilt it, I ended up getting an 05 Envoy Denali, slightly higher miles then my TB, so I'm interested in seeing how it does on oil.

 

[Vegacentralis]

First time user and first time truck owner here.
This oil consumption issue caused by the AFM is happening to my '12 Silverado 1500 5.3L, 120,000miles. Spark plugs #3 and #7 are fouled and misfire-it could be why I get only 16.2mpg. My mechanic said I might want to consider tuning to deactivate the AFM for $800. He's currently removing intake manifold to de-foul the motor and further investigate the cause. The '12 already has the baffled valve cover.
Is this "tuning" (reprograming the computer) something a GM dealer would do?
Has this corrected the fouling plugs and oil consumption problem for anyone (or improved mpg)?
It sounds like the classic, "more working parts means there's more that can fail"

And I don't feel or hear any noises when the motor deactivates 4pistons and switches from 8cyl to 4cyl.

 

[Sparky]

Please use the edit button when adding more info to your post, thanks!

I highly doubt a GM dealer would tune it out. And it doesn't cost $800 to do. Get yourself a Diablosport InTune and turn it off yourself for less than half that much.

16mpg from a V8 truck isn't that bad, depending on your driving conditions, habits, gear ratios, etc. I only ever got 18mpg out of my 07 (before I put bigger heavier tires on it), but then it also only has the 4 speed auto not 6 speed.

I started getting heavy oil usage around 130-something thousand miles (2 quarts in 3k). Tuned out AFM, and now usage is around 1/4 quart in 7000 miles or so. No MPG decrease or increase really.

 

[C-ya]

@Vegacentralis , you can get a tune from a member here for $100 (@limequat ) or you could get one from PMC of NC (I think that's the current name) for about $200-250, or you can get a Range OBD-II module that would disable DOD for about $200. (Wait a couple of seconds on that page and a pop-up comes up with a discount and free shipping if you have facebook.)

Like @Sparky said, I highly doubt a dealer will reprogram your ECM and turn a factory option off.

My motor was very quiet when it happened as well. I could only tell by listening to the exhaust note as I was passing a building, wall, or curb. Idling through town at about 25-30 and it would be active. Drop it into 3 and the exhaust sound would change.

 

[Mooseman]

If you want to temporarily disable it to see if it makes a difference, try this:
How to disable AFM/DOD at no cost
You will however get a CEL but you'll know what it's for. If it helps your situation, get the tune done. I also highly recommend @limequat at lime-swap.com.

 

[C-ya]

You are right, @Mooseman . I forgot about that, but there should be some way he can do the same thing on his truck since it is not a 360. But I bet there is a way. Also since he doesn't have a 360, lime-swap may not be much help unless he has a license for a 1500.

I missed your question earlier @Vegacentralis , about whether the tune helps. I went from 6 qts of oil between changes to 2-3 qts after the tune. It didn't hurt my mileage for sure... not sure that it helped. I'm getting 13.5 overall since I got my Trailblazer in Aug. of 2012. Summer I do better and winter is worse due to idling a lot.

 

[Mooseman]

An LS engine is an LS engine. I'm pretty sure he can tune it but it is a '12. More recent than anything else we've seen here.

 

[northcreek]

The "theory" is that the AFM delete prevents future excessive oil consumption. So you might be putting the proverbial "lock on the barn after the horse escaped".

 

[Sparky]

Depends on what part of AFM is causing oil usage. Mine wasn't apparently coked up rings since it stopped after turning it off. But yeah, if the oil usage is caused by rings, turning off AFM won't fix that. Some people have had success with an engine flush stuff to free up the rings if they're just sticking, and disabling AFM can prevent it from happening again. Other times, the rings can't just be cleaned up that way and the only fix is to pull the engine apart.

I was thankful that my oil usage was via some other path than that, even though I have signs of bad piston carbon build up on the driver side (still need to do another clean up attempt...).