Edmunds dealer partner, Bayway Leasing, is now offering transparent lease deals via these forums. Click here to see the latest vehicles!

Chevy Silverado and GMC Sierra Active Fuel Management Problems

12467…10

Comments

  • KCRamKCRam Member Posts: 3,516
    Since your issues don't involve the Active Fuel Management system, please post your engine question here: Chevy Silverado and GMC Sierra Gasoline Engine Problems and the suspension question here: Chevy Silverado and GMC Sierra Suspension and Ride

    kcram - Pickups/Wagons/Vans+Minivans Host
  • rangermitchrangermitch Member Posts: 1
    Were the problems with AFM resolved for the '09 and later models? Thank you.
  • minismomminismom Member Posts: 4
    I purchased a l500 sierra (l989) as a farm truck - this is what it is doing - it does not accelerate after stopping at an intersection - stalls & won't restart - have changed distributor & brians, plugs & wires, new battery, oil & gas filter - also when it does restart it belches black smoke and smells like gasoline - does the same thing when it is in reverse - sucks up gas like crazy - I don't want to have to have the tank pulled to change the fuel pump, screen or sending unit - the check engine light is on also - mechanic told me it was the catallyc converter - other than that it is a nice truck & the body & frame is in great shape for a truck that age - thanks for any help
  • obyoneobyone Member Posts: 7,841
    Sounds like you have a plugged catalytic converter. However, that may be the result of your problem rather than the cause. Since you stated that they have changed the brains, the other cause could be a bad fuel pump. The belching of black smoke and the smell of fuel is exactly what killed your catalytic converter. Your plugs are probably fouled at this point also.

    If you worked on the truck you could probably get away with $600 in parts to fix your truck. If using a mechanic you're looking at over $1000 to fix it. A replacement catalytic convter is close to $300 wholesale. Not sure if the truck is worth saving.
  • cnw20cnw20 Member Posts: 4
    I have an 07 Silverado with AFM and 5000 miles ago (I currently have 75K on it) the dreaded "add engine oil" light came and I had a dry stick. I took it to the dealer who replaced the gasket around the oil filter (you could see the oil accumulation on the bottom of the frame but surprisingly not a drop on my driveway - they told me it only leaked out at high speeds?) and added sealant to the bolts. Well 5000 miles later I have the same problem and am going back to the same dealer tonight - I'll keep you posted. Hey maybe if they fail to fix it this time I'll let it seize up and hopefully get a new engine?
  • gmcustsvcgmcustsvc Member Posts: 4,252
    cnw20,

    I apologize for the problems you are experiencing with your vehicle. Please keep us posted on any information from the dealership.

    Thank you,
    Caron, GM Customer Service
  • cnw20cnw20 Member Posts: 4
    edited August 2011
    I just called Chevy at 800-222-1020, didn't get a case # yet, and they will contact the dealer who "tried" to tell me that using 3 quarts in less than 3000 miles is normal - I told them when I dropped off my truck last night do NOT tell me this and they called today and did. There's many TSBs all over the internet on this lousy engine and GM knows it - I plan to fight this to the bitter end. If in fact, as posted by u earlier, that these engines are supposed to burn a quart for every 2000 miles that only means one thing - GM is again making garbage like they did in the 70s!
  • gmcustsvcgmcustsvc Member Posts: 4,252
    cnw20,
    Can you please keep me posted on what happens with Customer Assistance? I apologize for your frustrations. I look forward to your update.
    Christina
    GM Customer Service
  • tonygooch2000tonygooch2000 Member Posts: 2
    i got a brand new vortex max in 08 3 days after i got the truck i took it to the dealer to tell them about the knocking noise coming from the engine when the truck is running and a loud clicking sound when i make a u turn but the dealer was out of business so i took it to a other dealer they told me it was normal so i keep on driving until it became worst about 16,000k again they told me its normal then my friends told me its not normal because they all have the same trucks so about 35,000 i took it to a different dealer and they all said its normal mean wile i had lots of other small problems seat belt jam up door locks not work cruise control broke heated wind shell wipers not working and traction control broken so i drove the truck the ways it was until the engine blew up at 101,000k just over the warranty they fixed it under good=will repair then the same engine blew up 3 weeks later at 104,000k the guy from gm told me they would replace the truck or buyback the truck and had me take it to a dealer to confirm it was the engine so i did and some one else said they only gonna fix it again so far it cost gm over $20,000 to repair this shi# engine and i had to many things go wrong so i am pissed i will not expect this truck back at all and i demand a replacement truck and buyback this truck if not i will contact bbb about the and make sure non of my family or friend ever buy a gm product tonygooch2000@yahoo.com
  • gmcustsvcgmcustsvc Member Posts: 4,252
    tonygooch2000,

    I apologize for the problems you are experiencing with your vehicle. Do you currently have a case set up with GM Customer Assistance? If so, could you please email me the case number?

    You can get my email by clicking on gmcustsvc.

    Thank you,
    Caron, GM Customer Service
  • tonygooch2000tonygooch2000 Member Posts: 2
    ok caron i do have a case number and they are not doing anything. john the one who was handling my case assured me i would get another truck cause its obviously a lemon and now they are re nagging on they words. don't you guys record your phone calls? anyways it is noted in my account what he said. i dont wanna get mad but gm is screwing me. it cost me close to 42,000 dollars for this truck. i put 6,700 down and i am paying 800 for a broken vehicle. i know gm buys back their problem trucks. i want them to buy back my truck or i have no choice to go the arbitration route. please help. the case number is 71-969290786
  • flatfoot1flatfoot1 Member Posts: 3
    As it has been a while since my original Rant regarding my 2010 silverado and AMF . On the 5th return to the dealer, they determined it was cam shaft failure. After two days in the shop, they claimed a error msg. Showed up out of the blue stating the #1 plug fouled. I don't about you, but this is not my first run around with GM and the excuses for not doing the approbate repaired is getting old. so they replaced the plug and sent me on my way. Couple of weeks later the plug fouled again, this time it was asked with oil. They contacted GM for the third time. This answer was to pull the heads and remove the litters well long story short, on day two a different tech at GM to the dealer to replace the #1valve guide other then the valve cover being pulled pulled nothing else was checked. Don't know if I mentioned this before, my neighbor
    2010 at 18000 miles had engine rebuilt, cam shaft failure... Sounds like a common problem. Well the end of this story is the day after I got it back I traded it off at a 30%loss guess the value of
    GM's are not what they used to be. Replaced it with a 2011 chevy camaro. Dealer stated there are some issues ie... Exhaust system. But "GM" is refusing to pay for the repair as they state that is inherent to that type of system which is there because of the AFM. I think it time that GM stops trying to B.S. The government for the bad fuel milage and charge the penalty like Dodge does for not getting within the fuel guide lines. Thanks GM for finally getting it through my head, this is my last run around with a GM product as this company has no interests in the satisfaction of its consumer. On a positive note I have owned 78 camaro, 84 camaro four chevy trucks and my last 2011 camaro up to "2010 I had a good run.
  • flatfoot1flatfoot1 Member Posts: 3
    My 2010 silverado was diagnosed by dealer cam shaft failure after intervention from GM they replaced # 1 cylinder valve guide. That was the sixth attempt at a repair. Still didn't address the cam shaft. GM won't even take the word of the mechanics working on the trucks. My neighbors truck had engine rebuilt at 18000 miles, "camshaft failure" seem like GM Is trying to avoid a recall. I dumped the lemon
  • jbt4jbt4 Member Posts: 1
    I have an 07 GMC Sierra and I have also been having problems with oil consumption. At about 65,000 miles my "low engine oil light" came on. It had only been 1800 since my last oil change, there was no oil visible on the dip stick. I call the dealer where I purchased the vechile and they advised I bring it in as soon as possible. They changed the PCV valve, Manifold gasket and few other things. Everything was fine for two oil changes then the same problem started happening. I have an appoinment to bring my truck back to the dealership Monday (this will the 6th time) b/c the low oil light came on again and this time it had only been 1500 miles since my last oil change, I'm starting to think this problem will never be fixed and my 100,000 mile warrenty is all most up. Does anyone if there is a fix for this problem? Thanks
  • stumpman2stumpman2 Member Posts: 3
    edited August 2011
    I wonder if you bypass or reprogram the AFM where it stays in 8 cyl mode all the time if it will help? A friend who is a GM mech said they were having issues with replacing pistons due to this. said it wasn't lubing the cylinders properly that weren't firing/running when in 4cyl mode Just wondering if it will help or not?

    I have an 07 with 43,000 miles and so far no problems. Do all these engines have this issue after so many miles or just some of them?
  • gmcustsvcgmcustsvc Member Posts: 4,252
    jbt4,
    I apologize for your frustrations. Can you please email me with your complete contact information, VIN, current mileage, and involved dealer? I would like to set up a case for you with GM Customer Assistance. This will document your concerns and that you are experiencing them under warranty. Has the dealer involved technical assistance? If not, I would recommend asking them to do so. I look forward to your email.
    Christina
    GM Customer Assistance
  • chuck1chuck1 Member Posts: 1,405
    If you put it in manual mode and shift it to 5th - the AFM will never come on. You can try that.

    There is absolutely no truth to the fact they are replacing cylinders due to AFM.

    Read how it works-it's a very simple system-
    http://en.wikipedia.org/wiki/Active_Fuel_Management
  • stumpman2stumpman2 Member Posts: 3
    edited August 2011
    Mine is an 07 and doesn't have a manual mode that I know of.....Not sure why he would lie being it didn't have an effect on me. Said there were 5 in there being worked on or had been worked on. Said something about not getting enough lubricant to the cylinders or something to that effect.
  • chuck1chuck1 Member Posts: 1,405
    There are hundred of thousands of these motors on the road when you include all models of GM cars....

    Do a google search - see for yourself. I guess maybe a few have had problems. I couldn't find anything on a google search.
  • stumpman2stumpman2 Member Posts: 3
    Read on other GM boards many people are having issues with 07NBS and newer trucks using a lot of oil between changes and having engine troubles. Not hard to find at all if you look.
  • chuck1chuck1 Member Posts: 1,405
    It's not a lot of trucks. I understand, if it's yours its important. BUT, very few trucks are having oil consumption issues. I have looked at those other boards AND the NUMBER OF POSTERS who claim they are having issues.

    The vast majority are happy.
  • cnw20cnw20 Member Posts: 4
    Had it back to the dealer twice and its still using oil. They overfilled it for the first consumption test so after it burned that up I'm on my second consumption test now. Once I saw your (or another service person) post about a 5.3L AFM with under 36K miles should use 1 quart every 2000 miles I decided to trade it in and never buy a GM vehicle again. I have cars and trucks that had over 100K miles that NEVER used any oil between changes. When will GM finally realize that this engine is a lemon and do right by their customers? My guess - never.
  • dlhummelldlhummell Member Posts: 1
    I have a 2007 GMC Sierra SLT Crew Cab with a 5.3 AFM Motor. The day I drove this truck off the Dealer Lot in Jan. 2008 brand new it had multiple warranty issues.
    1.)Rear Power Window did not work.
    2.)Drivers Side Seat Motor did not work.
    3.)Whole Carpet Kit had to be replaced because of defect causing it to fall down under the brake and gas petal. They took out full interior trim and broke all clips that hold all plastic pieces in place.
    4.)Recall for Window Washer Heater. Causing Trucks to catch fire. Took it out and dissabled it.
    5.)Stering Wheel Control Lights would not work.
    6.)All 4 Door Handles Broke, almost off the truck.
    7.)Oil Dip Stick Tube broke away from the block at the bolt.
    8.)A/C Wire Harness to the fan blower motor.
    9.)Battery Replaced
    10.)Oil Consumption with AFM. They opened up the motor and put some coller on the AFM valve.
    Not even my first oil change since having the work done and it consumes again with the message coming on Low Oil.

    Local GMC Dealer " Phillips Buick GMC " Fruitland Park, Florida has been the ones to perform the repairs. On the second time in about the oil consumption I am being given the run around about it not being a problem. And they want to do a 1000 Mile test VS the standard 2000 mile 1 quart test. Even after the valve coller work to repair this problem, it still exists at the same rate.
    Along with the consumption issue I also noticed that my gas mileage went down. I complained of this as well. I haven't got more than 15 MPG on Highway almost since new. Sticker says 16 MPG City, 21 MPG Highway. After they did the work I got about 2.5 MPG more for about 6 tanks of gas. Then the gas mileage droped again and the oil low message came on again.

    I had such a problem with an aftermarket warranty that the original GMC Dealer " Fountain Auto Mall " Orlando, Florida,sold me. They sold me a $2,400 warrany that when I had to use it at Phillips GMC I was told that Phillips GMC would not honor it even though I bought it from another GMC Dealer. I also found out that the second warranty that I was sold ONLY provided the exact same coverage that the manufacture sold with the truck. 36,000 bumper to bumper and 100,000 drive train. I finally called the aftermarket warranty company and got $800 prorated back to me.

    I am currently consulting an Attorney for action against GM for the Lemon. And the original Dealer Fountain Auto Mall GMC for their deceptive practice of the useles aftermarket warranty.
    The firm that I am using is Krohn & Moss, Ltd. they will take a case for free if it is legit.

    I'm interested in any feedback anyone may have.
  • chuck1chuck1 Member Posts: 1,405
    edited October 2011
    I had such a problem with an aftermarket warranty that the original GMC Dealer " Fountain Auto Mall " Orlando, Florida,sold me. They sold me a $2,400 warrany that when I had to use it at Phillips GMC I was told that Phillips GMC would not honor it even though I bought it from another GMC Dealer. I also found out that the second warranty that I was sold ONLY provided the exact same coverage that the manufacture sold with the truck. 36,000 bumper to bumper and 100,000 drive train. I finally called the aftermarket warranty company and got $800 prorated back to me.


    I bought my truck and the dealer tried to sell me a third party warranty. The first question one should ask is "Is this a GM warranty?" Most of these third party warranty companies are "fly by night" and I don't blame the second dealer for not accepting it. There is a good chance they would not be paid by the warranty company. Dealers sell what makes the most money for them, not what is best for you. Good luck with the rest of your problems.

    BTW-you really over paid for that warranty.
  • fleurrivasfleurrivas Member Posts: 1
    Adding sealant to the bolt helps in some way, but the actual point upon which the leak comes out is in the gasket. I don't know exactly how does it happen after all you have firmly held the gasket. High speed, yes it is. It actually an aspect contributory to the leak. In my case, the built in turbo manifest such actuation. If you could have an engine less than what you are expected to pay off for the replacement, then go for it. But for me, I'd rather have it repaired.

    SecurantUSA
    Making the impossible possible!
  • string2string2 Member Posts: 71
    I feel like I have been ripped off by Chevrolet. I bought A 2011 Silverado Crew Cab two months ago. "The Active Fuel Management" system won't drop back to 4 cylinders at cruising highway speed (70 MPH) on flat level highway, unless going downhill or if I take my foot off gas. This is with or w/o cruise control turned on. AFM system will work for short distances at around 45 MPH. I have 2,700 miles on it now and it has never worked at highway speed, as advertised and explained in the Owner's Manual. Took to two dealers. There is no trouble code, but the computer was changed out. Still no improvemant at all. Contacted Chevy service assistant. She talked to dealer and said without a trouble code there is nothing wrong with it. She said drive it, it might get better if I put more miles on it. She said her decision was the final say on the problem. Checked videos on Utube and found a demo showing 95 miles on same truck as mine working just like the manual says it should. I am HACKED OFF @!*&#
  • cnw20cnw20 Member Posts: 4
    Once GM stated publicly that using 1 quart of oil for every 2000 miles is normal I sold my Silverado and since I do not a pickup anymore bought a 2012 VW Sportwagen TDI that gets 45 mph and I haven't looked back.
  • chuck1chuck1 Member Posts: 1,405
    The AFM will only come on at 6% or less throttle. It's not coming on if your driving 80plus on the Hwy...it's not going to happen.
  • string2string2 Member Posts: 71
    Thanks for the info Chuck. I have looked at the Demo videos on utube showing how AFM works. It showed V4 mode working as it should in cruise control at 72 MPH on level highway. Stayed in V4 mode about 3-4 minutes until starting uphill. Do you know if there is any adjustment on the throttle, that may be the problem? Thanks again!
  • chuck1919chuck1919 Member Posts: 176
    From what you are describing the road was probably level or perhaps slopes down a bit. It doesn't take much for it to "tune out" of 4 cyl mode because 6% is not much throttle.

    Even 80 on a flat road will not get you in 4 cylinder mode except going down a hill.

    I don't think GM should have ever put the V8-V4 indicator on the dash. Just let it go about it's business and nobody knows the difference. JMHO.
  • string2string2 Member Posts: 71
    Hey Chuck,
    Do you know if there is an adjustment for the gas pedal?
    You are also assuming that the truck doesn't have a problem. I have driven both ways on the same stretch of highway (no wind), over inflated the tires, upgraded to higher octane gas and no extra weight or passengers. If Chevrolet didn't show on the dashboard when the AFM is changing from 8 to 4 cylinders you couldn't pinpoint why the gas mileage is so bad because it is not activating a trouble code. Why cover up the fact that it is not working?? On the highway I am getting about one more mile per gallon that city driving 15 MPG). That's probably because of not stopping and accelerating
  • chuck1chuck1 Member Posts: 1,405
    I don't know if there is an adjustment. I will tell you on a recent trip form Salt Lake City, Utah to the Nevada state line I filled up and it was right at 20mpg. This included three mountain passes at over 6,000 feet in elevation. Then, from the Nevada State Line home to So. Cal the mpg was 18 1/2. (I drove a little faster across the desert).

    I have a 2011-5.3 Crew Cab with 2WD. I also have a tonneau cover which may or may not gain mpg.

    I am not downplaying your problem. All I am am saying at highway speeds the AFM will not come much on unless your going downhill. The truck weighs close to 6,000 pounds and it takes a little to move it along.

    Good luck on your issue.
  • gmcustsvcgmcustsvc Member Posts: 4,252
    string2,

    Sorry to hear about the problems with your vehicle. Since you have spoken with customer assistance, could you please send us your case number? We would like to look further into your situation.

    Thank you,
    Caron, GM Customer Service
  • string2string2 Member Posts: 71
    Caron, thank you for responding to my post.
    My service #: 71983951187
    I hope you have better luck than I am having trying to convience someone that I really do have a problem. Since my last post, I took the truck back to
    Ron Craft Chevrolet in Baytown, Texas. Mr Foust was a little more helpful on this visit and I am hopeful he will follow thru and help me. The following is that part of my documentation of the problem:
    10/18/2011 Afternoon - I drove over to Ron Craft Chevrolet and sat down to talk with Paul Foust. I explained that I was still having the same problem. He contacted someone referred to as a 2nd level Tech. at GM. He was referred to a document that he had not seen before (Document ID: 1995547). It describes how the AFM system works and some possible reasons the truck could be having this problem.
    Together, we did a test drive in the truck and used his hand held plug in computer diagnostic tool. He could see that the engine was not dropping back to 4 cylinders at highway speed except when there was a decline in the highway or when removing my foot from the gas pedal. His diagnostic tool also showed there was some sort of problem with the MAP and possibly the acceleration. He was unsure about how to address the problem. He ask me to call him on Friday the 21st.
  • string2string2 Member Posts: 71
    Caron,
    This is a follow up to my reply back to you yesterday. what I really need is a GM engineer, but it's next to impossible to get that level of service, for some reason?? If nobody knows how to correct the problem, why not????

    10/21/2011 11:15 AM - I called Mr. Foust at Ron Craft and left message. He Called me back about 15 minutes later. He said he had driven another truck on the lot, and it had a similar problem. He hasn’t been able to talk to anyone about how to correct it. Said he would call me back sometime next week. This has been dragging out like this for almost two months now.
  • gmcustsvcgmcustsvc Member Posts: 4,252
    string2,
    I have looked into your case and they are working on it. Thank you for your patience, I understand this is frustrating. I apologize for the inconvenience. Your dealer is researching this further with Technical Assistance. I recommend continuing to work with your dealer.
    Christina
    GM Customer Service
  • string2string2 Member Posts: 71
    Christina, Thank you very much for your assistance in trying to resolve this problem. I left my truck at the dealer for your GM engineer to check it out. To my disappointment and surprise, he said it was working okay.???? This I do not believe! It defies common sense. Why build and advertise the GM “ Active Fuel Management” system when it doesn’t work at the normal highway speed limit of 70 MPH (changing from 8 to 4 cylinders), at the very time it is most needed to get its highway fuel economy? I don’t think working at 66 MPH or less, for one minute, qualifies for working “okay”! Besides, who would want to take a chance on driving at LESS THAN 66 MPH on the open road and possibly get ran over by a fast moving truck. Also, it only worked for ONE MINUTE, and that was on a slight downhill grade (the rest of the time it wouldn’t be working at all). Please read the paragraph on page 9-40 of the 2011 Chevrolet Silverado Owner’s Manual, explaining the operation of the “Active Fuel Management” Driving and Operation. If this isn't double speak, then I don't know what is?
    Thanks again Christina for your attempt to help, but it looks like I won't be getting any assistance from GM. There really is a problem!
  • string2string2 Member Posts: 71
    Im in the Houston,Tx area. Does anyone know of a GM dealer who knows something about the 6% throttle or pedal setting on 2011 Silverado 5.3 engine, and how it relates to the activation (on/off) of the Active Fuel Management system. The dealers I have spoken with, know very little about it.
  • chuck1919chuck1919 Member Posts: 176
    AT 6% throttle or less the AFM kicks in - what are you trying to do or determine?

    The truck is drive by wire - so the trucks computer would in all likelihood control that function.
  • gmcustsvcsarahgmcustsvcsarah Member Posts: 1,964
    String2,

    Some dealerships I located in the Houston area include:

    David Taylor Cadillac Buick GMC (Phone 713.777.7151)
    Beck & Masten Buick-GMC Truck Gulf Freeway (Phone 713.947.4111)
    Demontrond Automotive Group, Inc. (Phone 281.872.7200)
    West Point Buick GMC (Phone 281.579.4300)

    If these aren't able to assist, the following link should help you find more dealerships in your area: http://www.gm.com/vehicles/dealerLocator.html#

    Hope this helps,
    Sarah
    GM Customer Service
  • string2string2 Member Posts: 71
    My AFM 2011 5.3 Silverado (8 to 4 cylinders) acts as though it's right at the verge of going into 4 cylinder mode at steady highway speed, but will only go there for maybe a second or two (infrequently) on level ground. Its like it just needs a small adjustment (somewhere) to make it stay in 4 cylinder mode. I know it won't work at 70+ MPH, but this is at 55-60 MPH. I've taken it to the dealers, but they can't find any trouble codes to tell them what to do. The dealers I have spoken with don't seem to know much about the AFM. If it doesn't show a trouble code, they don't know how (or have the time) to trace the problem. I'm just grasping at straws, the throttle may or may not even be the problem. If anyone is familiar with this problem, please let me know.
  • string2string2 Member Posts: 71
    Thank you Sarah, for the phone numbers from the dealer phone book. What I really need is a dealer, that you know for a fact, has delt with this particular problem and knows how to troubleshoot it without a trouble code. The ones that I have spoken with tell me to "bring it in" but without a trouble code, it's not likely they will be able to find the problem.
  • gmcustsvcsarahgmcustsvcsarah Member Posts: 1,964
    String2,

    I apologize for a poor response on my part – thank you for clarifying what you need. If you would be so kind as to send us an email that contains this information, as well as your vehicle’s VIN, we can ask our Technical Assistance Center for more information in regards to the AFM question you are posing.

    Again, I apologize for my earlier poor response and look forward to hearing from you.

    Best,
    Sarah
    GM Customer Service
  • string2string2 Member Posts: 71
    Purchased: 7/21/11 new at Ron Craft Chevrolet-Cadillac Dealer 4114 Hwy 10east Baytown, Texas 77521 Ph: (281) 421-3800 Service Mgr. Paul Foust email: paul.foust@roncraftautos.com

    This Truck is a 2011 Chevrolet Silverado Crew Cab, Engine: Vortec 5.3L V8 w/Active Fuel Management (AFM), Rear Axle 3.42 ratio, VIN# 3GCPCSEO3BG252186 (EPA Tested these vehicles) Their Average estimated fuel economy average was:
    CITY 15 mpg HIGHWAY 21 mpg (city is correct- Hwy 16 MPG, AFM has problem not going to 4 cylinder mode at hwy. speed, about 70 MPH (please see my prior posts)
    This fuel economy is advertised and touted openly by all the sales people at the different dealerships I contacted, including Ron Craft Chevrolet before I bought the truck.

    9/6/2011 - Called Chevrolet manufacturer 1 866 790-5700 x 21162 BECKY . She gave me a service #: 71983951187 -

    11/2/2011 Gm engineer finally looked at my truck this, as I previously posted.

    11/2/2011 Mr. Foust called for me to bring my truck to let the engineer look at it. I left it at Ron Craft about 9:30 and picked it up about 3:00 PM. Mr. Foust said the engineer checked the truck and they took it for a test drive. Mr. Foust said they could not get the AFM to change from 8 to 4 cylinders at the normal “open road speed limit” of 70 MPH, but they did get it to stay in 4 cylinder mode once, for one minute at 66 MPH . And the location where they were able to achieve that was on a very long and slight decline of the Hwy. on I 10 east near FM 146, close to Mt. Belview. To my disappointment and surprise, he said it was working okay.???? This I do not believe! It defies common sense. Why would GM build and advertise their “ Active Fuel Management” system when it doesn’t work at the normal highway speed limit of 70 MPH, at the very time it is most needed to get its highway fuel economy? I don’t think working at 66 MPH or less, for one minute, qualifies for working “okay”! Besides, who would want to take a chance on driving at LESS THAN 66 MPH on the open road and possibly get ran over by a fast moving truck. Also, it only worked for ONE MINUTE, and that was on a slight downhill grade (most of the time it wouldn’t be working at all). Please read the brief paragraph from the 2011 Chevrolet Silverado Owner’s Manual, p. 9-40, explaining the operation of the “Active Fuel Management” Driving and Operation. Is this not doublespeak, or what?
  • string2string2 Member Posts: 71
    Purchased: 7/21/11 new at Ron Craft Chevrolet-Cadillac Dealer 4114 Hwy 10east Baytown, Texas 77521 Ph: (281) 421-3800 Service Mgr. Paul Foust email: paul.foust@roncraftautos.com

    This Truck is a 2011 Chevrolet Silverado Crew Cab, Engine: Vortec 5.3L V8 w/Active Fuel Management (AFM), Rear Axle 3.42 ratio, VIN# 3GCPCSEO3BG252186 (EPA Tested these vehicles) Their Average estimated fuel economy average was:
    CITY 15 mpg HIGHWAY 21 mpg (city is correct- Hwy 16 MPG, AFM has problem not going to 4 cylinder mode at hwy. speed, about 70 MPH (please see my prior posts)
    The AFM and its fuel economy are advertised and touted openly by all the sales people at the different dealerships I contacted, including Ron Craft Chevrolet before I bought the truck.

    9/6/2011 - Called Chevrolet manufacturer 1 866 790-5700 x 21162 BECKY . She gave me a service #: 71983951187 -

    11/2/2011 Gm engineer finally looked at my truck this, as I previously posted.

    11/2/2011 Mr. Foust called for me to bring my truck to let the engineer look at it. I left it at Ron Craft about 9:30 and picked it up about 3:00 PM. Mr. Foust said the engineer checked the truck and they took it for a test drive. Mr. Foust said they could not get the AFM to change from 8 to 4 cylinders at the normal “open road speed limit” of 70 MPH, but they did get it to stay in 4 cylinder mode once, for one minute at 66 MPH . And the location where they were able to achieve that was on a very long and slight decline of the Hwy. on I 10 east near FM 146, close to Mt. Belview. To my disappointment and surprise, he said it was working okay.???? This I do not believe! It defies common sense. Why would GM build and advertise their “ Active Fuel Management” system when it doesn’t work at the normal highway speed limit of 70 MPH, at the very time it is most needed to get its highway fuel economy? I don’t think working at 66 MPH or less, for one minute, qualifies for working “okay”! Besides, who would want to take a chance on driving at LESS THAN 66 MPH on the open road and possibly get ran over by a fast moving truck. Also, it only worked for ONE MINUTE, and that was on a slight downhill grade (most of the time it wouldn’t be working at all). Please read the brief paragraph from the 2011 Chevrolet Silverado Owner’s Manual, p. 9-40, explaining the operation of the “Active Fuel Management” Driving and Operation. Is this not doublespeak, or what?

    I have read that if the accelerator/throttle is more than 6%, the engine will not drop back to 4 cylinder mode.
    My AFM 2011 5.3 Silverado (8 to 4 cylinders) acts as though it's right at the verge of going into 4 cylinder mode at steady highway speed, but will only go there for maybe a second or two (infrequently) on level ground. Its like it just needs a small adjustment (somewhere) to make it stay in 4 cylinder mode. I know it won't work at 70+ MPH, but this is at 55-60 MPH. I've taken it to the dealers, but they can't find any trouble codes to tell them what to do. The dealers I have spoken with don't seem to know much about the AFM. If it doesn't show a trouble code, they don't know how (or have the time) to trace the problem. I'm just grasping at straws, the throttle may or may not even be the problem. If anyone is familiar with this problem, please let me know
  • chuck1chuck1 Member Posts: 1,405
    edited November 2011
    The salespeople at the dealership oversell this feature. My AFM will not come on at 65 to 70mph. On slight downhill it does come on.

    MY average mpg (5.3-Crewcab) city is no more than 15 - usually less. The truck does get close to 20mpg highway if you keep it at 65mph and below and no head wind. 6% throttle is not very much - it takes more than that to move a 5,500 pound truck down the freeway.

    The AFM is highly misunderstood by both salespeople and the owners.

    I suggest renting another truck. It will probably be the same way. It's one thing to say it doesn't work correctly, do you have anything to compare it to?
  • string2string2 Member Posts: 71
    edited November 2011
    No I don't have anything to compare it to, other than what other owners of this type truck have told me when I'm at the gas stations. Some say they get 22-23 MPG. Also, the 2011 Silverado Owner's Manual explaination on page 9-40. And of course, what the new vehicle sticker showed when I bought it - average 15 City 21 Highway. What's really bad is, my nephew has a 2005 Silverado 5.3 crewcab WITHOUT (he says) Active Fuel Management. He swears he gets 22 miles per gallon. All the other trucks weigh the same as ours. It may be, you and I have a couple of lemons. I hope that's it. If not, we're all being deceived.
    It seems like GM could come up with an (approved) slightly modified ECM computer program that could be used in cases like ours. When they can't find a way to make them work the way the Owner's Manual describes. Most people drive faster than 45 - 55 MPH. (mine will only stay in V4 mode for short distances at 40 MPH) I don't understand the restriction? It's like punishing you for buying one of them.
  • chuck1chuck1 Member Posts: 1,405
    edited November 2011
    String,
    Honestly -I do not work for GM. There is a lot of misunderstanding regarding these trucks. There is NO WAY anyone is getting 22-23mpg with these trucks. These things weigh 5,500 pounds - it ain't gonna happen. Do a google search on the Ford F150s with the ECOTEC, even they are not getting that type of mpg.

    If your AFM is coming on going down hills - it's working. If it's not, then there is something wrong.

    I averaged 20mpg from Salt Lake City, UT to Mesquite, NV recently, and that was over three different 6,000 foot mountain passes. That's the best one can hope for.

    It always amazes me at the mpg claims made on the Internet. FYI-it happens on all forums for all makes. I don't know it must give some guys a rush to "stretch" the truth about the mpg.

    Please, if this concerns you and makes you unhappy, rent another truck and prove it to yourself. It's a truck and it isn't going to get stellar mpg regardless of what the dealers salesman told you, what others SAY they are getting, OR EVEN what the owner's manual says.

    If you driving a truck and not using it for towing, hauling - if it's just a grocery getter and your concerned about mpg, I am sorry you bought the wrong vehicle.

    Good luck - I wish you well.
  • string2string2 Member Posts: 71
    edited November 2011
    Maybe you do know more about these trucks than anyone else, including the writers of the 2011 Silverado Owners Manual and the EPA miles per gallon estimators. It's hard for me, though, to let the dealer sales people off the hook that easy. They represent GM. If you can't believe them, what do you do? Order direct from the factory? I don't need a truck all the time. Sometimes I need to pull an RV a couple hundred miles or haul some building material short distances. I bought the truck because it was advertised to get good gas mileage and would serve my needs to haul when necessary and use for transportation. I would then get rid of my old car. It would then serve both purposes. I'm sorry I bought the wrong vehicle too. You should be very satisfied with your truck if you are getting 20 MPG in the mountains, wow!. You must have one that works as it's should. You might not like it as much if your were getting 15.5 - 16 MPG on flat hwy (empty). With all your propaganda, are you sure you don't work for Chevrolet?
  • chuck1chuck1 Member Posts: 1,405
    edited November 2011
    "I don't need a truck all the time."

    15mpg is about right at 75 mph.

    If per your own words your using it for family transportation and not towing and hauling on a regular basis-you indeed bought the wrong vehicle.

    You would have been better off buying a Malibu and renting a truck for your occasional utility needs.
Sign In or Register to comment.

Helpful Tools

Most popular vehicles