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Chevy Silverado and GMC Sierra Active Fuel Management Problems



  • I remember I had a 2003 Silverado with the 4.8 engine. I dualled out the pipes and installed a flowmaster. At 50-55 MPH there was an incredible roar and vibration. Had to keep it above 60 to avoid it. Don't remember having the problem before the exhaust work.
  • Hi everyone!! my sister just bought a 2008 gm sierra 5.3 ,she has had it for almost 6 months !! and we are experiencing problems she said it was like the gas peddle just went to the floor on her!! she narrowly missed hitting a school bus and chose the ditch instead which ended up being the safest course of action but she did hurt herself !! we had the truck towed back to the dealership and they are now saying that they cannot find a problem for it !!!! If anyone out there has had any similar experiences please let me know as There is a problem and we need to get something done about this
  • Go to post #46,Mechanic can not reproduce the problem,Lets just wait till someone gets killed,I think gm should take the problemed trucks back.
  • Your lifters are losing prime have them replaced,but keep your ear on them
  • tafidtafid Posts: 12
    I thank you for that info, but I send you the same question I have been asking sense 300miles, now at 30k.

    RPM/Engine Surge:
    When easing to a stop or after stopping and slowly rolling (by easing off brake, no throttle apply) into my garage, the engine speed will increase surging the vehicle forward. It does not matter if the engine is cold or warm, nor driving for one minute or one hour. The engine speed will increase up to ~1000 rpm or more. The engine speed will surge and slowly come down to ~600 rpm in less than 15 seconds. This problem does not occur all the time, but I can bet on it happening each time I drive

    The dealer was told by Chevy Tech Service that it is normal. I can't see it normal to have the vehicle speed increase with my foot on the brake.

  • I bought the sierra 1500 5.3 and the problem gets worst, my is doing it oround 65-73mph that vibrasion is driving me crazy, its getting to the point that I have to let of the gas pedal because it just keeps doing it for miles.
  • obyoneobyone Posts: 8,054
    What does the dealer have to say about the vibration? Harmonic balancer?
  • I have a 08 silverado lt crew cab and would like to add the DIC control. I have taken the small dash panel off from the left side of the dash where the controls should be located, but there is no harness to plug the switches into. Is the plug located in a different location from where I am looking? GM is telling me this is not possible to do.
  • obyoneobyone Posts: 8,054
    If my memory serves me correctly the LT trim Silverado already has the DIC and is located near the steering column. The upgrade was being performed by owners who had the W/T and LS trim.
  • Has anyone heard a tick in the windshield.55 mph up tick,tick,tick.I have dent in my bumper from the lunge problem (hit a trailer hitch at a local walmart).Lifters are tapping again.I'm about to lose my temper.
  • gm said its normal its when it switches from 4 to 8, they are say its the change in exhaust tone, its driving me crazy.
  • well im glad im not the only one, i have an 08 sierra as well and i really didn't notice it until i drove it on a long trip, mostly on the highway is when you notice it, it seems like it does it once you maintain your speed for a little while, your driving and then all of a sudden you hear the vibration and im guessing that means that its in 4 cylinder mode, i HATE it as well it drive me insane. a friend of mine had his turned off and im probably going to do the same i bought a V-8 for 8 cylinders not 4 and to be honest with ya i think it is harder on the engine switching all the time. other than that i love the truck though....lots of space and lots of power(in 8 cylinder mode that is)
  • hey can u do me a big favor and find out how d they turn that feture off. I whant to turn it off
  • yeah the thing my buddy failed to mention was that he got his AFM turned off in Florida if you are near then then i can find out more in north carolina so that won't work for me.....i need to get that junk turned off cuz i can't stand it.....especially when im towing my boat....even in tow haul mode the truck doesn't no theres a big [non-permissible content removed] boat behind trying to read up on it as much as possible to find someone local who can do it.....maybe GM can do it prob not though im sure theres some loop hold that will void your warrenty......that being said if you find somewhere that does it let me know...and i will do the same for you
  • I got my 08 LT in January and it does have DIC. It is on the left side above the headlight switch.
  • I am wondering if anyone has a rough idle problem with the 5.3 w/AFM? I have seen several posts here with complaints about the 6.0 having a rough idle, but none really on the 5.3. I have a 2008 GMC Sierra that has a distinct shaky idle. The RPM needle does go up and down at times. I thought it was because the engine was just in the break in period, but I now have almost 3,000 miles on it and it hasn't improved. I don't know if it has to do with the AFM or possibly something else. My engine is the FlexFuel version, but it has this problem on gas or E85. It really gets annoying at stop lights. It gets worse the longer I idle. I'm beginning to wonder if I have an old carberated engine under the hood!!! Anyone else having this problem or heard of others having this problem?
  • usually the tick comes from the flaps on the sides of the w-shield

    i fix them by squirting sealant under the flaps and letting it dry

    it is easy to make a mess but easy to clean up when dry
  • uriasurias Posts: 1
    I have a 2008 silverado 2500hd 4X4, reg cab, eight foot box, 6 litre motor, 6 speed auto transmission with 3:73 are you guys doing for fuel economy...I am getting 13-14 city and 18 highway...what can improve this...have 17,000km on it
  • Hello. I bought the Diablosport Predator tuner and turned the AFM(DoD another name for AFM). Only tuner I know of that turns it off. Money well spent!!!!!!
  • have a 2007 sierra top speed 89 mph . smooth eng, no codes just won't go any faster than 89 mph. standed factory equip.
  • Hey. Wasn't sure if you were asking or responding to post...but if you are asking then the new Silverados have speed limiters on them. You'll have to get a programmer to turn it off. Just in case you were asking....
  • it was a post dealers say they don't know anything about it but there must be a limit on the max speed (89) do you know of a programmer that will do the job
  • The defroster on my 2008 sierra 1500 has too small of a vent to properly heat the windshield. Anyone else have this problem?
  • I just bought a 2009 Sierra with the 5.3 and FlexFuel and I'm having the same exact problem...there is a 200 RPM range difference at idle i went back and they re flashed the idle sensor and computer and it didn't help now it has to go back for a whole new throttle body. Its been doing it since brand new and i now have 1100 miles and its still doing it....It sucks because i want to put dual exhaust on it but it would sound stupid....GM really needs to step up there game here...ive been a loyal gm owner since i was 16 and this really left a sour taste in my mouth....$36K for junk.
  • My first Silverado was a 2000 4.8, did not have any vibration issue, upgraded it to a 2004 5.3 Silverado, in 2007 started to develop vibration on idle and at about 65MPH on the freeway. Took it to the dealer three times spent about $250 to replace varous parts, no cure.

    At the end of 2008 received a court ordered notice from GM regarding a class action settlement on the engine vibration complaint for 1995-2003 all Silverado V8 models.

    Recently traded in my 04 5.3 in for an 09 4.8, decided to stay away from the 5.3 for now until they figure out the issue.
  • brucesacbrucesac Posts: 1
    Hello all. Here is my quick question. Just purchasing the above mentioned vehicle and getting pretty poor mileage, I'm just trying to find out how I know if the AFM is even working. I read the posts about adding the Driver's Information Center but my dashboard doesn't even have the spot on the left hand side like people are saying. Anyway, since this is the "low end" work truck without the bells and whistles, I don't know how to determine if the AFM is working on this 5.3L engine. I can't feel any difference in the engine and we just took it on a long trip and averaged about 16 MPG using cruise control the entire way. Any help and/or suggestions would be appreciated.
  • I have the AFM in my 2005 TB EXT and it's been giving me problems since I hit 60,000 miles. It fouls out the plugs in cyl. 1,7,4,6 every 5000 miles or so and creates a plume of blueish smoke only when cruising down the highway and it kicks in from 4 to 8 cyl. No smoke any other times than that. i now have 150,000 miles mostly from the highway.
  • dyma82dyma82 Posts: 4
    I am having EXACTLY the same problem on my Silverado 2007 5.3. Mine is not flex-fuel...gas only. I know mine has the AFM because I can see it switching from V-8 to V-4 and back while driving on the highway.

    Have you figure it out?

    I want to take it to the dealer, but I would like to learn a little more about this issue before. I don't trust dealer's tech personnel. I have had very bad experiences with them, leaving me with the feeling that they don't really know their own product very well. Thus, I try to avoid trips to the dealer as much as possible.
  • wildcat82wildcat82 Posts: 3
    I haven't figured it out yet. I have a mechanic doing a search for me to see if there is a way to disable the AFM. Mine is not flex-fuel either....I'm thinking that the solenoids that control the locking pins are not operating properly and allowing oil to leak into the cylinders in shutdown mode. Must be a way to shut it off through the computer.
  • dyma82dyma82 Posts: 4
    I get the feeling that the AFM is not the source of this problem (Rough Idle...I mean, it is a very gentle shaking while idling. However, even though it is very subtle, it is very, very annoying and unexpected on a 34K truck).
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