Chevy Silverado and GMC Sierra Active Fuel Management Problems



  • bprepdahbprepdah Member Posts: 1
    Can anyone tell me where the EVAP canister is located on an '06 Silverado Crew Cab?
  • chevyfan1969chevyfan1969 Member Posts: 3
    Really good post Gmax. After much debate, I just purchased a 2008 1500 Vmax. I was originally planning on buying a diesel, either a Dodge or Chevy, but after thinking about it I backed out of a diesel altogether. I just couldn't make the initial cost ($6500 extra) plus the premium on fuel work out on paper. I can buy ALOT of gas for that amount. Sure, I've heard alot of people tell me that a diesel will work alot longer, but I don't plan on keeping it for 500,000 miles anyway. Anyway, I've put about 700 miles on it so far and am very happy with it. I've read several complaints about fuel mileage, excessive shifting, stutter when going in & out of AFM, and rough idle. First, my mileage sets at around 18 mpg on average which I think is great for a truck that has the capabilities that this one does. If you want fuel mileage, buy a 4 cylinder. There's always trade-offs when it comes to power/ mileage. I thing GM has done a good job at coaxing 18 or so out of it. I was really expecting closer to 13-14. I do have the excessive up/ down shifting when climbing a pretty good hill but I've noticed that the reason that it does that is, when it downshifts, it has enough torque to quickly get it back up to speed, causing it to shift back up. I would suggest if that is a problem, drop the shifter down to 3rd to eliminate the "problem". As far as noticing it going in and out of AFM, it's very slight. The only reason I notice it is because it's a new feeling that I'm not accustomed to yet. The idle is defininately a little rough, but I think it's cool. All ponied up engines have a rough idle that I've been behind. All in all, I think it's a great truck and I can't wait to hook on to my trailer and see what it'll do. Anyway, just wanted to ad to your post.
  • jboehmjboehm Member Posts: 44
    I have driven a couple of different Silverado/Sierras with the Acitve Fuel Management. One thing I have noticed is that, when sitting at a stop light, the AFM will switch from 4-cyl to 8-cyl. Can someone explain why? (I know that I have seen documentation that that is the way it is suppose to work but I cannot locate a reason why).
  • tafidtafid Member Posts: 12
    I have the same problem. I notice that the rpm increases as well. If I stop, open the garage door, ease off the brake, occasionally the truck will surge up to 900-1000 rpm. Chevy tech service says it is normal, but did not explain why.
    How can it be normal to have your foot on the brake and the vehicle rpm increase and vehicle surge forward?
  • obyoneobyone Member Posts: 7,841
    Chinese multilevel marketing? Give me a break. Spam by any other name is still SPAM!!
  • astroman2astroman2 Member Posts: 1
    I have a new 2008 Sierra with 5.3l engine and about 2,000 miles. Once every week or two, when starting the engine, it sounds like none of the lifters have oil in them. The engine sounds like an old model V8 with mechanical valve lifters that are way out of adjustment.

    The valve clatter will continue but goes away by shutting off the engine and Immediately starting it again. The oil pressure is good and the dip stick shows oil is full.

    The noise only happens when the engine is cold or warm. Is AFM in control of the lifters and valves at startup?

    Has anyone had this problem?

  • natesmsnatesms Member Posts: 20
    I have the 6.0 in my Silverado and I have noticed that to, but very breifly on start up. It sounds exactly like you describe but goes away in a couple of seconds. I don't have to shut it off and back on.

    Let us know if you find out anything.
  • obyoneobyone Member Posts: 7,841
    The dealer will tell you that this is normal and happens more often with the 6.0 for some reason. For myself, it would disturb me. But what can you do?
  • raymazraymaz Member Posts: 1
    I have the 1500 5.3 with AFM and have noticed an inconsistent vibration at about 55mph. There's a flat smooth stretch of highway I often take going home for about 7 miles and the vibration often occurs there between 50 and 55mph. It feels like I'm going over a course road surface but I'm not. AFM is sometime on and sometimes not. This vibration always occurs when I maintain this 55mph +/- speed for a time. It never happens in town and I have never noticed it at 65+. I've never ntoiced it at idle. Other than that I like the truck a lot. I'm a boring old fart of a driver but I get very good mileage. The lowest fillup I did gave 16.6 and highest has been 22.4. That 22.4 was almost all highway driving. Considering the power and size of this truck I think that's superb.
  • obyoneobyone Member Posts: 7,841
    50-55 mph is where most of the resonances in a vehicle converge for some reason. That's why there's no vibration at 45 or 65 but keep it at 55 mph and you've got a bumpy ride. This is usually attributed to the tires.
  • asylum575asylum575 Member Posts: 72
    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.
  • misswenchmisswench Member Posts: 1
    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
  • rednecktroyrednecktroy Member Posts: 8
    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.
  • rednecktroyrednecktroy Member Posts: 8
    Your lifters are losing prime have them replaced,but keep your ear on them
  • tafidtafid Member 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.

  • jess20jess20 Member Posts: 3
    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 Member Posts: 7,841
    What does the dealer have to say about the vibration? Harmonic balancer?
  • mikef15mikef15 Member Posts: 1
    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 Member Posts: 7,841
    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.
  • rednecktroyrednecktroy Member Posts: 8
    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.
  • jess20jess20 Member Posts: 3
    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.
  • BeefnutzBeefnutz Member Posts: 2
    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)
  • jess20jess20 Member Posts: 3
    hey can u do me a big favor and find out how d they turn that feture off. I whant to turn it off
  • BeefnutzBeefnutz Member Posts: 2
    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
  • skimm99skimm99 Member Posts: 1
    I got my 08 LT in January and it does have DIC. It is on the left side above the headlight switch.
  • hunter9296hunter9296 Member Posts: 1
    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?
  • toywrenchtoywrench Member Posts: 1
    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 Member 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
  • santaman58santaman58 Member Posts: 3
    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!!!!!!
  • powdercoater3powdercoater3 Member Posts: 3
    have a 2007 sierra top speed 89 mph . smooth eng, no codes just won't go any faster than 89 mph. standed factory equip.
  • santaman58santaman58 Member Posts: 3
    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....
  • powdercoater3powdercoater3 Member Posts: 3
    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
  • jason5817jason5817 Member Posts: 2
    The defroster on my 2008 sierra 1500 has too small of a vent to properly heat the windshield. Anyone else have this problem?
  • 09sierraz7109sierraz71 Member Posts: 1
    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.
  • jacmyoung2jacmyoung2 Member Posts: 20
    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 Member 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.
  • wildcat82wildcat82 Member Posts: 3
    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 Member 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 Member 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 Member 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).
  • wildcat82wildcat82 Member Posts: 3
    Mine isn't a rough idle problem; just a plume of smoke that only happens when cruising on the highway and I start to accelerate. Like I said before, I get no smoke any other times and the only plugs that foul are cylinders 1,7,4,and 6 which are the ones that shut down during AFM.
  • bspinz9bspinz9 Member Posts: 2
  • bspinz9bspinz9 Member Posts: 2
    hey guys i got a 08 silverado crew 5.3L Z71 ltz w/ 10k on it
    & im just wondering if anyone is having this same problem when putting the vehicle in reverse (from drive only) there is a significant 3-5 sec. delay basically leaving me stranded in the middle of the road on a 3 pointer
    i've been to the dealer they updated the flashdrives for motor & tranny etc..
    & still does the same thing & as usual its within the GM tolerance haha.
    tranny fluid levels are normal & i was just thinking if & i know this sounds out of this world ridiculous the afm has anything to do with it i wanna shut the afm off i think it just effects the total performance of the motor. I've been a long time gm owner & the 04' 5.3L is a monster thats why i stuck with the 5.3
    & besides that ticking noise after 60mph the truck is a great truck

    oh 1 more thing can the afm be shut off by a tuner & is the hypertech tuner worth it
    thanks in advance guys

    "i just think afm shouldn't be a option when buying a truck a truck is a truck for power & balls fuel management is for the 4bangers & buy american we gotta keep this country alive & trucks is the reason why "
  • obyoneobyone Member Posts: 7,841
    Save your money with the Hypertech. There are better tuners out there for the same price.
  • dyma82dyma82 Member Posts: 4
    Hi hunter9296, have you find anything new about this condition?

    I am having exactly the same issue with my 2007 Silverado 5.3 (Not Flex-Fuel).

    Thanks for your time.
  • rednecktroyrednecktroy Member Posts: 8
    Have the inside windshield piller trim replaced,The tck will go away for a while.It'l come back after a while.There should be tec service bulletine for this problem.
  • rednecktroyrednecktroy Member Posts: 8
    Soft lifters and valve springs is where the rough idle problem is,I bought a stethascope to find that there was a faint tick on my right bank,cold starts the tick or miss is more audible hold the peddle to the floor it gets louder.Then take it to your highly educated mechanic,let him tell you its piston slap knock,argue with him till he actually goes out to hear the problem.It took me 45 minutes to get my point across.The lunge problem is when the computor is in relearn mode it has a glich,for sure.
  • dyma82dyma82 Member Posts: 4
    I agree. Soft lifters could actually explain this problem (shaky idle), and reinforcing the theory is the fact that additionally to the shaky idle, my truck has always been affected by another issue, which is definitely caused by soft lifters (since it was 54 miles old). The other issue being: If I left my truck unused for more than two days, when I start it on the morning of the third day the engine sounds like a very bad diesel. Then little by little the lifters recharge and the sound goes away. It does it 3 times out 5 times I leave it unused for more than two days.

    I am trying to gather as much info as possible about this issue, its cause, and the solution, so that by the time I take it to the dealer I can “try” to get something useful out of them.
  • owns5chevysowns5chevys Member Posts: 1
    My 5.3 ltr 2008 Silverado runs great, but just doesn't cool effectively. The AFM seems smooth to me, and it makes good power for a 5.3 ltr engine. But long grades on the Freeway cause the temp to keep rising. I have to turn on the heater full blast, and slow down, to keep the gauge from continuing on up. I have had a few puzzling electrical problems, including stabilitrac system errors that are intermittent - wondering if the computer controls the electric fans ? and maybe that is the common root cause of my problem ? But the AFM works good - just not good gas mileage (around 12.6 to 13.2 mpg). Any hints from anyone ? Anyone else have cooling issues and low mileage ? (I have about 8000 miles on the truck now)
  • littlemaclittlemac Member Posts: 1
    dont know if you solved your problem or not but i had a similar problem with my 01 and it turned out to be the fan clutch. very easy to replace.
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