2010 Silverado concerns

Discussion in 'Performance & Fuel' started by SoCalSilverodder, Feb 22, 2012.

  1. SoCalSilverodder

    SoCalSilverodder New Member

    I have a 2010 crew 4x2 silverado 5.3 with the AFM, 29k miles. Some issues y'all can hopefully help me out with:

    1) I get 15.5 mpg according to DIC regardless of highway or city. I baby it to death and I have a very light foot. Is this normal mpg?
    2) It shifts in and out of 4 cyl mode constantly in traffic under 35 mph and sometimes I have to depress the accelerator 1/4 down to get it to go back to 8 cyl. On occassion, when it switches, it makes a chunking noise. I can only explain the sound like going over a cattle grate at highway speed (I live in SoCAl now but grew up in the country, hehehe). Are these normal conditions for the AFM?
    3) When Im at part throttle, I hear a buzzing sound from under the dash or in the tranny tunnel. It goes away when I ease up on the throttle and/or accelerate harder. Any suggestion where this might be coming from?

    I had an 07 with zero issues and 18 mpg. Traded in hoping for a better experience.

    Please help with your comments and suggestions and hopefully I can solve these issues and keep this one for the long haul. :(
  2. ajarman

    ajarman Epic Member 5+ Years ROTM Winner 1000 Posts

    Double Post.

    With the 6spd you should be getting better than 15.5 mpg with being really easy on it. No dash lights on?
  3. SoCalSilverodder

    SoCalSilverodder New Member

    No code. no light. Nothing.
  4. ajarman

    ajarman Epic Member 5+ Years ROTM Winner 1000 Posts

    All stock? Intake, exhaust ect.....
  5. mfleetwood

    mfleetwood Epic Member 5+ Years ROTM Winner 5000 Posts

    Just curious.....Are your 20" wheels stock?

    Check out these two links to see what type of MPGs others are getting.

    I personally have never had a problem with my AFM before I turned it off via my Diablosport Predator tuner, but because of my custom tune, it made sense to shut it down.

    Here is also a thread containing ideas on how you can increase your MPGs.
  6. sstoner911

    sstoner911 Epic Member 5+ Years 1000 Posts

    Have you asked the dealership if they have any TSB's....sometimes they will have an update or 2 for things like AFM.
  7. AMac

    AMac Rockstar 3 Years GMTC Chick 500 Posts ROTM Winner

    I have 20" wheels stock on my 2011 and am getting about the same as SoCalSilverodder. I did put an aftermarket exhaust, flowmaster 40series, on and no help. I'm not sure if the cap on my truck helps or hurts my MPG issue but either way around 15 is crazy. Similarly to issue #2 in SoCal's list I also on occasion hear a clunking noise when I let off the accelerator. I'm thinking this is in the drivetrain and have been trying to monitor when it does/does not happen.
  8. mfleetwood

    mfleetwood Epic Member 5+ Years ROTM Winner 5000 Posts

    AMac - The reason I asked if the 20" rims were stock is because if the total diameter wheel/tire size increased (I guess I should have asked if the tire size was factory as well), then the DIC would not be calculating the mileage correctly since the speedometer would be off. To me, it sounds like the MPGs are low and I was trying to see if there could be some simple reason, especially because the vehicle is so new. I agree with you that an exhaust is really not much help toward increasing MPGs. Additionally, from what I have read, tonneaus and caps can help slightly...however, the cap shouldn't reduce your MPGs unless the weight of your cap is more of a detriment than the marginal benefit you gain from reducing wind drag.

    As far as the clunking....I have heard that complaint from many and most seem to tie it to the AFM. Unfortunately (and luckily), I have not experienced it. Because your ride is still under warranty, you may want to consider taking it to a dealership and see what they say. At a minimum, you should be able to find out if the AFM is causing it and if it's something else, they should fix it for free.

    btw...nice looking ride!
  9. AMac

    AMac Rockstar 3 Years GMTC Chick 500 Posts ROTM Winner

    Thank you. I do understand that putting on an aftermarket wheel package would affect the DIC and while the wheels are stock I thought the tires looked a little wide. I will have to make it a point to take a look at the wheel specs to see if it is possible that the previous owner did an upgrade.

    Again, the clunking does not happen all the time but I will keep an eye on it. I think the drive-train warranty is 5 years.
  10. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Since I bought my 2011 Silverado I've been doing a lot of studying about the AFM system in preparation for modifying my truck and through trial and error and a few questions at a very reputable GM garage I've found out the AFM system is very particular.
    #1 If you change tire sizes at all you need to have the computer tuned for the new tire size.
    #2 If you replace any part of the stock exhaust again you need to have the computer tuned.
    #3 If you replace the airfilter with a free flowing airfilter, have the computer tuned.
    #4 Clunking noise is normal, the transmission seems to have a clunk when it downshifts from 6 to 5, no ill effects have been noted from this yet, its just a noisy trans between 5 and 6.
    #5 Some drivers have noted a lag and/or clunk when driving slow and speeding up, GM attributes this to two things, 1 the transmission catching up, it slips a little due to the traction control system, and 2 the drive by wire throttle isnt as responsive as expected. Some drivers have reported better throttle response at slow speeds with the traction contol turned off. Problem is not all trucks are equiped with an On/Off switch for the traction control.
    #6 Some drivers have reported throttle issues at speed, the vehicle doesnt speed up as fast as expected, this too is attributed to the drive by wire throttle and it's responsivenes.
    Hopefully some of this will shed some light on a few of the issues your facing.
    I am surprised at the mileage your getting though, most of the 2wd trucks are getting between 17 and 19mpg, I've been averaging 18 with mine which is why I'm reluctant to do any mods to it, so far I havent seen any modifications available that help out the MPG.

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