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2010 Silverado with strange symptoms

Discussion in 'Chevy Silverado Forum (GMC Sierra)' 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. mfleetwood

    mfleetwood New Member ROTM Winner 1000 Posts

    Double thread...Mod, please remove.
    Last edited: Feb 22, 2012
  3. Coach24

    Coach24 New Member 1000 Posts



    what does your dealer say?
    it should be a warrantable check

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