2010 Chevy Silverado AFM Engine Problems or not??? Fuel mileage? 5.3 engine AFM

Discussion in 'Chevy Truck Talk & GM News' started by Gvnitup, Dec 9, 2011.

  1. Gvnitup

    Gvnitup New Member

    I have recently purchased a 2010 Silverado with a 5.3 with 35xxx miles. When I test drove the vehicle it drove great. Now that I have had it a few weeks I have noticed it seems to make different sounds mainly I think when the active fuel management starts working. I am not getting that good of gas mileage, I was hoping for 18-19, I am however getting 16-17. the truck is bone stock. I have been trying to drive half way decent to see what the highest mileage is I could get. I have started to notice that when you are coming off of cruising thottle to accelerate it makes different noises almost like a skip.

    i know it isnt skipping, otherwise it would log a dtc. My question is, Why kind of mileage is everyone else getting? i never see a light or indicator when the afm is working. Is this normal on this model ? I have read alot of posts where people wanted the afm removed simply because of the different sounds or feeling when it works. i dont mind so much, i would care less if I were getting better mileage.

    Just a little about myself, I am a master tech we lost our gm badge right after obama made gm obama motors. (we were one of the medium dealers that got a pink slip). I do however currently have a tech2 in the truck, we dont have access to tsb's now. But, I have all kinds of toys to play with. . i have been working on gm's for over 10 years mainly medium duty, aka duramax etc. . I can help myself, and have no major complaints with the truck. Since I am a tech by trade and am not familar with the system it's driving me insane when it works and there is no indicator. Just looking to see how the system works for everyone else. Any and all input would be greatly appreciated.
    Last edited by a moderator: Jan 24, 2013
  2. Coach24

    Coach24 New Member

    Similar experience. Also when it cuts back to v4 I get a vibration that seems to be getting worse. Unfortunately my dealer can not duplicate the feel.
    With 20,000 miles I get an average of 17. I find going downhill the v4 doesn't always kick in.
    This is with meticulous upkeep, air pressure is double checked every Saturday. Oil changes and washes are religiously performed.
    Best MPG in one trip was 18.3.
  3. Gvnitup

    Gvnitup New Member

    Thanks for the reply. I seem to be getting the same. I really wanted a full size, but purchased a canyon new instead (price). Now, I am not quite so sure it was a good trade. I love the truck, and have been a chevy guy all my life. having said that, I reset all of the fuel trim data, and learned data and the issues toned down. I'm not saying they are gone, But maybe for a little while anyway.
    Do you have a light that tells you when its going into v-4, i only ask cause I do not. I can however see which cylinders its cutting off. While monotoring the tech two it cuts off different cylinders on decel, cruise, etc. I have noticed that it constantly cuts them off even if you don't feel it.
  4. 747

    747 New Member

    From what Ive read, 17 average is pretty normal. You should be able to see when the V4 mode is active. Do you see the 4 buttons aligned vertically on the left hand side of your guages (on LS and LT)? Push the top button, and it will give you different kinds of vehicle data.
  5. aloxdaddy99

    aloxdaddy99 New Member

    if you have the DIC you can cycle through the buttons and one will show which mode you are in.
  6. Gvnitup

    Gvnitup New Member

    My dic dosent have that. I only have the trip reset type dic. I dont have the buttons to the left of the steering wheel. When I cycle through it shows trip, oil reset, compass, trans temp, and mileage.
    I am going to the dealer to have remote start programmed (since I can no longer program through tech 2), i am going to ask if they can program any extra abilities.

    ---------- Post added at 05:48 PM ---------- Previous post was at 05:46 PM ----------

    Mine is a 2010 lt 5.3 6 speed flex fuel
  7. Welcome to the club. I would buy one of the Diablo tuners and turn the afm off. People that I know that did this saw no drop in fuel mileage.
  8. BIGGBOB

    BIGGBOB New Member

    my 2011 5.3 gets 15 to 16 city and on highway 20 and if your on a long flat road with cruse you can get 22. (3:42 rear end)
  9. tbplus10

    tbplus10 Moderator

    I've only had my 2011 Silverado a week and have 370 miles on it but one thing I noticed right away was a sort of lag when changing throttle positions, where I noticed it a lot is when coasting in V4 and giving more throttle it tends to lag like a small hiccup then accelerates and changes to V8 mode.
    Other 5.3's with AFM I test drove had this same hiccup so I assume it's normal, I have 18" wheels on mine and did notice a truck I test drove with 20" wheels had more of a lag to it. Hadnt noticed any noises associated with the different modes.
  10. Gvnitup

    Gvnitup New Member

    I got 18.5 last week, This week i got 13.5 Not real sure what thats about. Filled up tonight, if I get that horrible again will have to back up and punt.
  11. krp2nite

    krp2nite New Member

    Your numbers are in line with what I get. I have kept track of every tank of gas since new through an app on the iphone and overall the total average including all trailer hauls and everything the average mileage after 38,000 miles is 16.8. If you don't have the DIC--You can add it for $80 and less than 2 minutes of install time it will allow you to see when the truck is running in V4 mode and V8 mode while driving. Plus it keeps track of your average and instant fuel mpg numbers.
  12. Gvnitup

    Gvnitup New Member

    I have the stick beside the speedo that allows me to view mileage,oil.change info etc
    If I add the buttons on the side it will allow me to view more without programming?
    It wouldn't seem like chevy would do something that simple. As far as mileage I have got 16 .5
    18.5 and 13.5. Not sure why on the last I just figured it was bad gas.
    Please let me know about the dic panel. Thanks
  13. tbplus10

    tbplus10 Moderator

    Something I had to clarify with a GM mechanic before posting, if you turn off the AFM, or do any programming with a tuner it shows up on the "Logged Entries" in the trucks computer.
    This is a permanent log of all actions that happen that affect the computer, it cant be erased so if you say put a custom tune in and change it back it wont show what the tune was or what exactly you've done but it will show the technician that there was an action completed.
    I'm not sure of what all information they can get from this or if it could be enough to affect Warranty.
  14. dadngt

    dadngt New Member

    I have a 2007 NNBS 4.8 no AFM. Bought the truck bone stock with 21k miles. now have 42k. I was getting best 19mpg. so trying for better, I picked up some alloy wheels new tires still 17 inch just not steel wheels. Added a flowmaster exhaust, new air filter, oil changes when needed. & with those few efforts I'm getting 15 mpg. What maintence is needed at 40k? I have also noticed the tag on the side of the fuel pumps have a -2 rating for the fuel. Used to be in the + side so we're also getting crappie gas.
    Last edited: Dec 31, 2011
  15. CKNSLS

    CKNSLS New Member

    Real World mpg from a return trip from Salt Lake City Utah to Southern California-

    Salt Lake to Mesquite Nevada (3 -6,000 foot mountain passes) driving 75 to 80mph= 17.2 mpg (AFM hardly ever came on-to be expected)
    Mesquite Nevada to Southern California driving 70mph w/cruise control on 95% of the time= 21.2 (AFM came on a lot)

    No surprises here - speed kills the mpg and does not allow the AFM to come on.

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