RPM bounce or fluctuation at constant speeds (PI0680)
December 29th, 2014 | 10:49 AM
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RPM bounce or fluctuation at constant speeds (PI0680)
Hi all, I just bought a 2008 Suburban LTZ this past weekend and noticed that I see RPM minor fluctuation at constant speeds usually around 50-55mph. I did a bit of searching and found the below info but I wasn't sure if this was applicable to my trunk and/or if there is a fix for it. Anyone have any ideas? Thanks.
#PI0680: Random Needle Movement or Engine RPM Increase while Driving at Steady Throttle on 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 (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.
source: http://www.silveradosierra.com/vorte...-t9475-10.html
#PI0680: Random Needle Movement or Engine RPM Increase while Driving at Steady Throttle on 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 (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.
source: http://www.silveradosierra.com/vorte...-t9475-10.html
December 29th, 2014 | 11:36 PM
#2
Official GM Rep
Joined: Mar 2010
Posts: 4,163
Likes: 25
From: Global Headquarters in Detroit, MI
Hi all, I just bought a 2008 Suburban LTZ this past weekend and noticed that I see RPM minor fluctuation at constant speeds usually around 50-55mph. I did a bit of searching and found the below info but I wasn't sure if this was applicable to my trunk and/or if there is a fix for it. Anyone have any ideas? 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.
source: rpms fluctuating : Vortec 5300 5.3L V8 - Page 2
#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.
source: rpms fluctuating : Vortec 5300 5.3L V8 - Page 2
Very sorry for these concerns with your vehicle, and if you do decide to bring it into the dealership, please do not hesitate to reach out to us in a private message. We would be happy to reach out to them on your behalf. We look forward to hearing from you soon.
Patsy G
Chevrolet Customer Care
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March 12th, 2012 9:15 PM