Joined
·
36 Posts
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
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
