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2011 Silverado, POOR mileage, surging, no check engine light

13

Comments

  • chuck1chuck1 Posts: 1,405
    HALF TRUTH ALERT!

    String the AFM isn't working IN YOUR TRUCK. It's working in the other half million units on the road. My truck included. I can consistently get 20mpg at 70ish with the AFM activated on the highway.
  • string2string2 Posts: 71
    Okay Lucky! Go ahead and rub it in! We know yours works like it's suppose to. The only way you could be getting 20 mpg is for your AFM to be working in v4 as it should at hwy speed. But I would like to know how you came up with those conclusive facts that every GM truck, but mine, works like yours and is averaging 20+ MPG.
    There are many, many GM truck owners who have never visited any website. There are at least 14 reported posts on this website that say they are also having problems, not to mention complaints on other websites or those that didn't post their complaints at all. I know how they are supposed to work (like yours). All these trucks should get that kind of gas mileage. However, I think you have to agree, these complaints should represent a considerable number of problem GM trucks on on the road.
    You have helped to make the point for me and the other problem GM truck owners though. As you have just acknowledged, yours is operating normal!

    GM tells me mine is working normal at 16 MPG on flat highway @ 65 70 MPH without the AFM working at all. AND, they won't try to fix it.

    By the way Chuck, does your truck have 6 speed transmission or 4 speed automatic trans.
  • chuck1chuck1 Posts: 1,405
    "By the way Chuck, does your truck have 6 speed transmission or 4 speed automatic trans"

    The "clunky" six speed. (Yea, mine clunks too!)
  • daninrapidandaninrapidan Posts: 5
    edited October 2012
    Purchased my 2011 Silverado 1500 LTZ Crew Cab October of 2011. The first 7000 miles were at 17.7 miles to the gallon. AFM worked perfectly. About 7500 miles the voltage guage started doing the dip below 14v on the guage, and I noticed the trucks mileage started dropping. Then the misshifts, hesitations, coughing, started. I also noticed how HOT my garage was getting after parking the truck in it, you could hear the tinging of the metal cooling down from the exhaust system. I had mentioned the poor running condition to the dealer and was told it was probably bad fuel. I choked on this for a while, and then the soot on the tail pipe started as the mileage dropped. Complained, to no avail, normal normal. .... Labor Day 2012, I bring the truck in and say no more, something is wrong. No codes, but they noticed that the Alchohol content is reading 0% all the time, and the fuel in the truck is 15% Alchohol. They re-learn the Alchohol content, and the truck is normal until the very next tank, which happens to be Ethanol free fuel. Im back to the poor running condition again.
    Fast forward to 14k miles. Im down to 13.3 MPG, clunking all the time, and its surging like Im being rear ended. This truck does not like to coast at all, resuming any acceleration causes it to hesitate.
    Service department says that they see what my complaint is, but cant fix anything because corporate says its working as designed and wont let them do anything. This "anomale" only happens to be on the 2011 1500 AFM product line. Thing is, they say the delay they put in the accelerator is normal, and its to save all the torque from being dumped on the transmission. Obviously with it the hesitation getting worse, the torque placed on the trans (the clunking), the worse the trans gets.. how is this delay or hesitation helping my transmission again GM ???? 46,000 dollar Mistake is all I keep saying to myself, should have kept the 2006 Ford that got a consistant 15 MPG towing or solo. This is the Last GM product I will ever buy with this kind of lack of integrity from Corporate. Obviously reading here, there are alot of other people that are having the same exact issue with their trucks ...... if anyone is watching, I would love to know what gear ratio the trucks with this issue are equipped with.... Mine has the 3.42's ???????????
  • chuck1chuck1 Posts: 1,405
    About 7500 miles the voltage guage started doing the dip below 14v on the guage, and I noticed the trucks mileage started dropping.

    The alternator has a energy saving feature that turns it down when the system is not needed.
  • daninrapidandaninrapidan Posts: 5
    edited October 2012
    Not needed ??? when has 9V been the same as 12V ??? If you have ever wrenched before, and changed an alternator, battery or starter, you will see that the manufacturer or re-manufacturer states Voltage must be 12.7 for them to guarantee their parts. Starter manufacturers would prefer you replace the battery at the same time as the starter....

    Of course its normal, Im well aware of the alternator doing this, we have a 2007 and 2008 3500 Duramax, 2010 1500 LTZ, 2011 1500 LTZ ( this one ) and a 2012 1500 LT, so Im well aware of the issues of these trucks, Im saying that my PCM has probably more issues since this voltage drop, and trust me as much as that needle drops, it also pegs max out to the top of the line they drew so that they dont have to explain this "feature" , they can point and say "NORMAL" just like everything else is "normal"
    GM tends to take a great idea and over complicate it. What possible mileage gain can be seen thru turning off an alternator ??? That same gain gets lost when it has to work twice as hard to pump up a weakened battery. Also, my power inverter HATES this voltage drop and will not power up my laptop on trips as the voltage is too low, as it sees that as a battery drain .. Dealer says ... so what, its not our power convertor and wasnt sold as a chevy option......
    As a computer technician, I can tell you how many PC power supplies in both desktop and laptop computers I replaced due to faulty power supplies. Problems disappeared once the computer got "clean" stable power. Computers that are underpowered get unpredictable, and you cant tell me an automotive PCM is not the same as a regular computer, its more of a specific task oriented device... but they are pretty much the same animal running on the same 12V DC platform.
    What amazes me is, Our $46k cars are not our own anymore, the corporation still owns them and will tell you how they are supposed to run and deny any claim if they can pin it on something else....... In this case, the delay they say should be there is .006 sec upon stepping back on the throttle, and Im saying its a full 3.0 seconds, thats a HUGE difference, one that can be felt most of all about 20- 35 MPH ( school zones, traffic conditions, curvy roads ) and YES, the dealer READ verbatim the blurb from GM about the .006 second delay ...... his response was to stop "tromping" on the gas pedal, well you cant tromp on the pedal in bumper to bumper traffic !!!!!!!!!!!

    OH !!!!!!!! yes, I was also told the heavy soot on the tailpipe was caused by a non GM chrome tip on the exhaust, to my reply of - its part of the Z71 chrome package shipped out from the factory with it on.... stopped him dead in his tracks on that, but he said he would check for a "bulletin"
  • chuck1919chuck1919 Posts: 176
    You should be driving a 1960s model. That way you could change you plugs condenser and points every 12000 miles. Your frustration is you need to buy 100k worth of computerized equipment to work on your truck.
  • We have a G30 old church van, 355,000 miles with a 350, and the old TBI system. 1000 lbs of tools in it, and on regular unleaded its getting 15 consistantly.

    The 600$ programmer that will fix the issues, I should not have to spend, as well as violating my warranty. Not for a sticker price on THIS truck of over $46k. To be by the service department and the mechanic that GM has built these hesitations into the sub routine in the computer to "save" the transmission, and the EPA wont allow them to fix it is utter bull ****. Why is my GM vehicle running worse than the first 7500 miles ??

    I would appreciate only useful comments on the issue, what or who fixes the problem permanently. At this point, my brother is right, find a decent older truck, and dump 46k into repairs and upgrades and have a real vehicle.
  • daninrapidan,

    If you're not already working with Customer Assistance and wanted for us to check into this further with you and your dealership, please email us at socialmedia@gm.com (include your name and contact information, a summary of the situation, the last 8 digits of your VIN and mileage, and the name of your dealership).

    Sarah, GM Customer Service
  • chuck1chuck1 Posts: 1,405
    Here is a useful comment for you. Do a search on the internet and find out exactly what the characteristics of these transmissions are. Then, you can make make an informed decision on how to proceed.

    1) You can see if others are having the same issues.
    2) You can see if they have been able to have them fixed.

    It will lessen your frustrations.

    I already know the answers to these questions.
  • ceb66ceb66 Posts: 70
    daninrapidan,

    Check the transmission forum on this site for very, very similar issues.

    Potential General Motors' truck buyers; test drive these trucks extensively at 45 mph and see if they clunk lag growl or bang as the active fuel management moves from 4 to 8 cylinders.

    Check for slop in the rear end.

    Let us know if you're told "it has to adjust to your driving habits." Right from the GM "play book"!
  • chuck1chuck1 Posts: 1,405
    Yes,
    Please test drive them. They are a great value. In most major markets $10,000.00 discount off sticker is very common. GM sold over 50,000 units (Silverado/Sierra) in September of this year. The YTD totals so far are 410,381 units!
  • Im not interested in your comments Chuck, stay off my post. Glad you are happy with your Silverado, I am not..... Your comments are NOT helpful, in fact they are down right annoying... You're hawking these threads like you personally build these things and are upset there are people with LEGITIMATE complaints. Customer service has gone down hill in not only GM, but most major companies... Im tired of paying the price for someone else's shortfall, and corporate greed. I work very hard for my pay.

    If you are so happy, start your own thread saying so, Im sure you can find at least 12 others that will agree with you. Furthermore with the hundreds of review, and forum web sites with these problems being discussed, if there were only 12 per site, thats still alot of unhappy people...

    In manufacturing there's typically 5-10% of a product that does not work properly. Thats where customer service comes in to play ... making those people happy again. To be dismissive is not a correction, but a cover up.

    Enough said, Im getting rid of my silverado at a very high cost to me.

    Lesson learned

  • string2string2 Posts: 71
    edited October 2012
    Let us know if you're told "it has to adjust to your driving habits." Right from the GM "play book"!
    =====================================================

    Hey ceb66,
    I was told "the trucks computer system has to learn your driving habits" the first time I took my 2011, 1500 crew cab into the dealer at around 1700 miles. The AFM wasn't allowing the motor to drop back to 4 cylinders above about 65 MPH on level highway. It now has about 12,500 miles on it, and it still hasn't learned my driving habits. Every time I talk to them, they come up with some other reason why it won't work, including "it's working normal"
    I went over to the used truck dealer and drove two just like mine. One had 46,000 miles on it, the other 16,000. They both drove just like mine (which is different than the 2011 Silverado Manual explains). It explains that these vehicles should operate in v4 AFM mode well above 70 MPH on flat lever highway, at steady speed without an excessive load (Full details can be found in GM's shop manual)
    These truck computers must be real slow learners, but I'm afraid mine will need to be put in the Insane Asylum (pretty soon).

    $34,500 for a truck that gets 15 MPG in town & 16 on the Highway. Talk about getting screwed!!!!!
  • ches31ches31 Posts: 3
    I have a 2011 gmc 1500 I have been back 5 times to the dealer for brake problems and truck shaking from the rear. I have had it. I should have spent the extra money and got the ford. I have filed with the state under the law. Nice looking truck but I am done...
  • chuck1919chuck1919 Posts: 176
    The AFM will not come on well above 70mph. That's about when it cuts off. It will not come on at 75 unless going down a hill.
  • string2string2 Posts: 71
    Please read my post again,

    I went over to the used truck dealer and drove two just like mine. One had 46,000 miles on it, the other 16,000. They both drove just like mine (which is different than the 2011 Silverado Manual explains). It explains that these vehicles should operate in v4 AFM mode well above 70 MPH on flat lever highway, at steady speed without an excessive load (Full details can be found in GM's shop manual)
    ====================================================

    My point was that the GM 2011 Silverado Owners Manual does not indicate there is a speed that AFM should quit working. Also, GM's shop manual Document ID # 1995547 explains in detail the parameters for the AFM to work properly. With everything working properly, the AFM should be working if the engine speed is between 700 and 2800 RPM's. That's if you are running on flat highway at a steady speed and not pulling a load. My 5.3 engine turns at 17 - 1800 PPM's at about 70 MPH. Of course, that's in V8 since it won't change into v4 mode above about 65MPH without going down hill or taking my foot off the gas. If I keep it at the hwy speed limit of 70 mph it wont change unless there is a low spot in the road. That's why I'm only getting 16 MPH on the road. The other two used trucks I test drove did not work at 70 miles per hour either.
    On the open highway is when the AFM really needs to be working to get the EPA estimated gas mileage shown on the window when you buy the vehicle.
    GM had one of their engineers look at my truck and said "it's working normal" and they will not correct it?? BUYERS; LET THIS BE A WARNING, (This problem will not trip a trouble code) MAKE SURE IT WORKS AT 70+ mph BEFORE YOU BUY! If the AFM works at 70 MPH in cruise control on level highway-buy it. It will probably be one that works like it should. The six or seven that I have tested do not. I hear there are some that work like they should.
    I have explained the complete details in previous posts.
    Mine is not getting any better at 12,500 miles. I'll be trading mine off this week. It's a good truck if you don't mind the mileage, I just can't afford it at 15 MPG City & 16.1 (Pure Hwy miles). Do your homework and Good Luck!
  • chuck1919chuck1919 Posts: 176
    edited October 2012
    String
    Seriously I am glad you are in a position to finally off load your truck. I know it has been a source of irritation for you. If you don't mind me asking-what will be your next vehicle?

    I am assuming it will not be another truck because most get no more than 15 or 16 around town and no more than 20 on the highway-since your issue really boils down to gas economy.

    In addition I have over 3000 miles of open highway cross country trips and 20 mph is very acheivable-but the AFM WILL NOT come on above 70-75mph. I don't care what the shop manual says or your short test drives on the highway. You can validate your decision to trade in your truck anyway you want. The sales tax and license you will end up paying will buy quite a bit of gas-especially considering you obviously are not driving a lot of miles.
  • string2string2 Posts: 71
    I am assuming it will not be another truck because most get no more than 15 or 16 around town and no more than 20 on the highway-since your issue really boils down to gas economy

    =====================================================

    Chuck,
    Thanks for wishing me well. I would not be selling my truck if I would have gotten 20+ MPG as the window sticker showed when I bought it. I normally drive a vehicle for a long time and 15 city and 16 hwy. is no good, too me anyway. That's not what I bought and that's not what I want. As you state above. I shouldn't have any trouble finding one that will get at least 20 MPG on the hwy.
    If GM won't correct this problem, what else will they deny if I have another problem in the future?
  • chuck1chuck1 Posts: 1,405
    edited October 2012
    String-
    Please consider the following:

    6000/miles a year (assuming HALF your 12,000/yr miles driven will be highway)

    6,000/miles a year divided by 16mpg=375 gals of gas 375x$4.00/gal for gas=$1,500.00

    6,000divided by 20mpg=300 gals of gas 300x$4.00/gal for gas=$1,200
    Assuming 10 year ownership

    1,500.00 x 10/years=$15,000.00
    1,200.00 x 10/years =$12, 000.00

    So this is what your talking. The truck is getting it's rated city, you knew that going in. The truck isn't getting it's rated highway (which you didn't know). It looks like an emotional decision-it doesn't pencil out financially-IMHO.
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