Rpm surge bounce-----need some real help

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by alkaspeltzar, Jul 31, 2013.

  1. alkaspeltzar

    alkaspeltzar Member

    Hi everyone, I got a 2010 5.3L w/6 speed w/66,000 miles.

    Recently it started having this "rpm bounce" , about 100-200 rpm when driving about 40-50mph. The rpms are low since the truck is in its 5th or 6th gear, typically around 1000-1500rpm.

    I have had the TPS relearned, new air filter, MAF and throttle body cleaned with no luck. Wondering if it is spark plugs or tranny.

    I have had to the dealer and of course, they see nothing wrong. Clearly, it never did this. It is not even accelerating or decelerating, just holding speed and it is bouncing. I am thinking tranny not staying locked in.

    I have ran into a bulletin from GM about rpm surges due to V4-V8 mode, but this is not the same. It does it in M5(AFM deactivated) or drive, and i can clearly see the rpm bounce when it says "V8 mode".

    ANy suggestions, i am at a loss and dont want to keep spending money with the dealers to hear "it is normal" or "drive it till it breaks". IF you are GM Customer serivce, please give me real help from GM DIRECT....not another dealer connection.

    Thanks
    #PI0680: Random Tachometer Needle Movement or Engine RPM Increase while Driving at Steady Throttle on Level Road at Approximately 50-55 MPH - (Feb 23, 2012)

    Subject: Random Tachometer Needle Movement or Engine RPM Increase while Driving at Steady Throttle on Level Road at Approximately 50-55 MPH

    Models: 2010-2012 Cadillac Escalade Models
    2010-2012 Chevrolet Avalanche, Silverado, Suburban, Tahoe
    2010-2012 GMC Sierra, Yukon, Yukon XL
    Equipped with 5.3L, 6.0L or 6.2L AFM Equipped Engines (RPOs LMG, LC9, L76, L94) and 6L80 or 6L90 Automatic Transmission (RPO MYC, MYD)

    Condition/Concern
    Some customers may comment on a random tachometer needle movement while driving at a speed of approximately 80-88 km/h (50-55 mph) with a steady throttle on a level road. They may also comment about hearing an engine tone change as engine RPM briefly increases and then decreases. Customers may occasionally describe this condition as a surge, flare or shudder.

    Recommendation/Instructions
    This condition may be caused by normal Active Fuel Management (AFM) transitions. When the engine cycles from V4 mode to V8 mode, the engine will produce increased torque and as a result the TCC slip speed may increase momentarily. This increased slip speed may be visible as movement of the tachometer needle or audible as an exhaust note change. This AFM transition from V4 to V8 mode and back to V4 mode is normal operation. The resulting small increase or decrease in engine RPM is also normal.

    To diagnose if the random tachometer needle movement is caused by AFM transition, shift the transmission to manual mode (M), select 5th gear (M5) and drive the vehicle under the same conditions. Selecting M5 manual mode will make AFM inactive and the engine will stay in V8 mode. If the condition is eliminated when AFM is inactive, it is normal operation and cannot be eliminated. No repairs should be attempted.

    - - - Updated - - -

    Here is a video to check out. You will see when it locks into V8 mode, at 50 mph, in 6th gear, it bounces about the thickness of the needle. Thanks

    http://videobam.com/FqVHF
     
  2. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    If you have tried the 5th gear in M test and it still revs, the AFM (as you suggest) is not your problem.,

    I suspect you have a torque converter that is not staying locked up.

    Check the torque converter relay.
     
  3. j cat

    j cat Rockstar 4 Years 1000 Posts


    I hope you get this all resolved .

    this comment to GM customer service I find a common complaint. I guess they think you do not have a yellow pages .

    no special help for you from them to fix anything . no documents / TSB , or any past repair history .

    just a marketing ploy , like GM is really concerned you have a problem .
     
  4. GM Customer Service

    GM Customer Service Rockstar 4 Years 500 Posts


    Hello,

    I am sorry to hear that you are experiencing an issue with your vehicle. We do value as a loyal customer. I would like to look into this for you. I norder, to research your concern I will need you to private message me your VIN and preferred dealership.

    Best regards,

    Jennifer T.
    GM Customer Care
     
  5. IronBear

    IronBear New Member

    I'm having the very same issue as alkaspeltzar. My truck is a 2010 Chevrolet Silverado Crew Cab, 5.3L with only 46K miles.

    Iin addition to the light hesitation upon take off.

    Please help!
     

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