alkaspeltzar

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 they see nothing wrong. Clearly, it never did this.

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".

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.

MDTAHOE

Pull #1 and #7 spark plugs out ( first and last ones on drivers side) and take a look. Report back if they look abnormal (compared to another cylinder)

alkaspeltzar

Can i ask why #1 and #7 cylinder? Is there something known that affects/wears these spark splugs for some reason?

And if it was miss, would the truck pick this up?

Thanks, i will try regardless.

MDTAHOE

Bulletin No.: 12-06-01-001B

Date: June 01, 2012

Subject: Service Engine Soon Light On, Rough Running Engine, Cracked or Oil Fouled # 1 and/or 7 Spark Plug

Models:
2007-2011 Cadillac Escalade, Escalade ESV, Escalade EXT
2007-2011 Chevrolet Avalanche, Express, Silverado 1500, Suburban, Tahoe
2007-2011 GMC Savana, Sierra 1500, Sierra Denali, Yukon, Yukon XL, Yukon Denali, Yukon Denali XL
Equipped with Gen IV V8 Engines

Built Prior to February 1, 2011

Supercede:
This bulletin is being revised to update the Parts Information to remove a part number. Please discard Corporate Bulletin Number 12-06-01-001A (Section 06 - Engine/Propulsion System).
Condition

Some customers may comment on a service engine soon light being on and/or rough running engine. Technicians may find DTC P0300 set. Upon further investigation, technicians may find cylinder #1 and #7 spark plugs oil fouled and/or the porcelain may be cracked or broken on the combustion chamber side.

Cause






This occurs on the driver's side (left side) of the engine due to PCV pullover that adds additional oil to the cylinders that can foul out or damage the spark plugs.

Correction

Important
If Corporate Bulletin Number 10-06-01-008C has been previously performed, then a new valve cover may not need to be installed. Please look for the second design baffle with the square hole at the end of the baffle.
Install a new left valve cover with the revised baffle to prevent PCV pullover that adds additional oil to the cylinders.