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12-09-2011, 08:27 PM #41
I will not tell anyone they are nit picking as my 2011 only has 130 miles. My 5.3l is running fine, I did notice a little shutter when idling after delivery. Remember your truck has a VVT motor. Gas quality and octane will effect it's performance. My last truck had VVT and the difference between when my wife filled it from near E to full with 87 to my usual fill of 93 was very noticeable. With a non variable cam shaft octane increase has near no effect unless timing and other inputs are adjusted manually. I have also noticed with my time as a tech in the military; A computer controlled trans and motors learn inputs from a driving style and use those regular inputs to tailor your vehicles performance.
Example, the first Gen up armor Hummer, had an new updated brain that not only controlled the trans up and down shift set points, it all so controlled fuel/throttle. When a new driver would jump in and have a drastically different driving style, the dam thing would go into "safe" mode. An operator was stuck in no higher than 2nd gear while the truck computer was "protecting it's self". We would get a recovery call, tell the operator to park it reach behind the driver seat and hit the reset button. Being a GMAC design this was the first real world application with the Allison trans. So, if your driving style is more often to cruse the vehicle it will adopt that as the desired setting, thus drop into V4 and as your finding. It's just not meant for the sudden bursts of low end grunt, especially if your running low octane fuel. Now your fighting driving style and the VVT.
My self, I'm a lead foot and that is how I'm breaking in my vehicle. I have since filling with 93 and jiving a nice short skinny pedal jab have noticed the truck is jumping to a low gear as soon as I'm near full stop. They do learn, ask if the dealer can wipe the memory, or start running higher grade gas if you want better performance.
Another consideration is where you are buying your gas from; We have what we call "res gas" up here in Buffalo, NY. While it's cheap on the reservation, the quality is bad and contains lots of water and lots of water absorbing chemicals. As a Ford dealer tech years ago, I have personally removed fuel filters with what looked like tooth paste in it. It's not just the "res" either. Some station tanks either leak ground water in them or are older poorly insulated, condensation and poor maintenance lead to bad quality gas. If you think weights and measures keeps a close eye one quality, your mistaken. Some stations in my area have had three and four owner changes over the thirty seven years I've been in Buffalo. Guess how many have serviced their holding tanks, guess which ones I don't fill my truck at.
I am in no way convinced that GM dose not still need to tweak this system, and that it's all or none of the above, it could be a combination of many factors. Good luck and good hunting, no for an answer is not an answer. Hound your dealer and GM till you get what you paid for. If this problem becomes more and more a pain for them and enough people bitch, the fixes follow.I am a American solder, I am a member of the finest fight force on earth, I am the bump in the night. I will defend the United states of American Against all enemies both foreign and domestic. Repent now all those who would do my nation and it's people harm; For when we come it will be too late.
2011 GMC Sierra SLE, Z71 with 5.3 l and max tow/haul package
12-10-2011, 12:27 AM #42
Thanks for your service to this great country of ours!! Congrats on the new truck.
12-10-2011, 09:33 AM #43
- Join Date
- Dec 2011
After reading this post, it has shed alot of light on my issues. being that I have some tools others may not. I will reset the learned data, compare the driving of the truck . Try the difference between grades of gas and report. I am just curious, I know several people with the same engines just a few years older that does not have afm. What fuel mileage is everyone getting?
Also, having worked on allison transmissions for several years I can confirm the clunky noises. However you will be hard to find a better trans.
12-10-2011, 08:24 PM #44
running 87 from the gas station on post (army exchange gas) ive been getting around 15 on post, 20 plus highway. m,ods are in my sig. i try to stay out of the skinny pedal for the most part, but i romp on it a fair bit as well.
2011 GMC Sierra SLE 5.3 Z71 4X4 Stealth Gray Metallic / 2004 Chevy Impala LS 3.8 Cappuccino
Tow mirrors - Diablew Tuned - Flowmaster Regular 40 - Ready Lift 2.5' lift - BFG LT A/T K/Os - Carr Light Wing - TruckLite LED lights - Optima Red Top - 50% Front Window Tint - Line-X bedliner - Airaid MIT - Tekonsha P2 - ARS Billet Grill - Fia custom fit seat covers
12-18-2011, 07:45 PM #45
- Join Date
- Oct 2011
I am absolutely shocked at the number of AFM problems listed here. It hearkens back a couple of decades when Cadillac came out with a cute little gizmo called "The HT400". It was supposed to save all the Caddy owners lots of gas because the drive train would just shift to 4 cylinders powering the car. If I remember correctly, most of the owners just put normal engine and trans in their cars because the "HT400" was mostly a disappointment. Sounds like GM has resurrected that late 70's\early '80's gizmo shop and foisted it on the consumer again.
I really feel for those who put their money down and make their payments. That's a lot of commitment and investment from the consumer in the "New GM". Too bad GM is unwilling to really get involved and correct the problem.
Currently my wife drives a '08 Cobalt - the best 4 cylinder I've ever had. I have a 2011 K3500 4X4 with about 5500 miles on it. It tows the TT and hauls the ATV's I'm mostly happy with it.
After reading stuff like this, I'll probably look to the other guys when replacements are needed.
I feel for those AFM owners. I hope my luck holds out
Last edited by bsmntcritr; 12-18-2011 at 08:02 PM.
12-18-2011, 08:15 PM #46
BSMnt - Sadly, your post is yet another example of the same half truths that have generated over 1,000 posts by 14 posters on another forum, some of whom have migrated here. Today's AFM has very little to do with what you call the HT400 technology that is outdated by decades. I suggest educating your self and doing a google search.
Many owners here (including myself) have reported the AFM as seamless. Remember, GM sold 45,000 units (combined Sierra/Silverado) in November. I suggest you talk with the other 44,986 owners and not the 14 that spew half-truths about GM and their trucks.
12-18-2011, 08:21 PM #47
having a 2000 silverado 4X4 for 11 years with well over a 100,ooomi and having no oil consumptions or poor mpg , why AFM ?
I get 19 mpg @70 mph hywy ...16-17 mpg around town driving... I use synthetic engine and tranny fluid with 87 octane fuel.
I have read at the 30,ooo to 50,ooomile point the engine start sucking up a good amount of engine oil with the AFM..I have read that the diablo tuner does have the ability to turn off and on this feature. for a few hundred , I would give it a try rather than have engine damage.
so far the only fix is to disable AFM , the dealerships seem to have no idea how to control this GM experiment.
12-19-2011, 05:08 AM #48
- Join Date
- Aug 2011
No problem here, I also find the AFM seamless on my 2011 Silverado. No Quality or Performance problems.
2011 Silverado Ext. 4X4 5.3 Z71, 18" Wheels
12-19-2011, 08:03 PM #49
- Join Date
- Oct 2011
WOW - again
Are you GM rep or Company rescuer?
I don't need your suggested research. I was alive and living when that HT400 load was delivered. I've owned a '74 full time 4x4 model that GM foisted on the public. Remember those? 9mpg on a good day!
You would suggest GM is somehow not imperfect. Please, you should do some research on the lack of warranty support GM has given to their customers.
I honestly hope GM and their dealers can step up and resolve the AFM issues some speak of here. I really do.
I, however, am also cognizant that GM is a for profit company and will protect the bottom line before the customer. Perhaps you could devote a little time for research check into how those retired GM workers were treated when GM failed.
Last edited by bsmntcritr; 12-19-2011 at 08:05 PM.
12-19-2011, 09:39 PM #50
There are many people looking at uncertainty in regards to their pensions. Just ask a number of various state, city, and county workers across the country. Back on topic - there are not that many AFM issues, it is not widespread. There are still those who wish to find every GM internet board on the net to complain about their perceived issues, rather then spend $300.00 on a custom tune.
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