Impala Forums banner
1 - 2 of 2 Posts

·
Registered
Joined
·
598 Posts
Discussion Starter · #1 ·
Hey guys, I've been noticing a slight shudder / vibration coming through (mostly) the steering wheel, but also through the gas pedal when my car happens to be in 3-cylinder mode. It's kind of like driving over rumble strips, but it's nowhere near as bad. It is especially obvious when I'm cruising around 40 mph and very light throttle is being applied, keeping my engine in the 1,800 RPM range, more or less. It goes away once 6-cylinder mode is activated.

Is this normal? Searching teh interwebz has shown that some people think its normal, whereas some people think it's not. I think there was a TSB out for the LZ8 version of the engine, also 3.9 AFM but non FlexFuel, detailing a similar problem, which I will quote below. Should I just go ahead and replace the MAP? Any advice is greatly appreciated! Thanks.

Chuggle, Surge or Shudder
By techeditor on December 1, 2007 7:52 PM
Some owners of a 2007-08 Chevrolet Impala equipped with 3.9L (LZ8) Active Fuel Management Engine (VIN Code R) may comment about a slight chuggle, surge or shudder that occurs when the vehicle is in ovedrive and traveling at a steady speed in the 38-45 mph (61-72 kmh) range. The condition is most obvious when a very light throttle is applied. The very lightly applied throttle is not enough to cause the torque converter clutch to release or the transmission to downshift.

Set the Driver Information Center (DIC) so it displays the Instant Fuel Economy and Active Fuel Managementâ„¢ indicator. Drive the vehicle as described above while observing the Active Fuel Management indicator. When the condition occurs, you should observe that the vehicle is operating in the 3 cylinder mode and is not switching to the 6 cylinder mode when the very light throttle is applied.

The Manifold Absolute Pressure (MAP) sensor may not be interpreting the engine vacuum signal correctly. If this is found, replace the MAP sensor.
 

·
Registered
Joined
·
598 Posts
Discussion Starter · #2 ·
Update, I changed out the MAP sensor. Didn't solve the shudder. Maybe it's just the way the engine is under those conditions? (Light throttle, 3-cyl mode, 40ish mph)

Anybody have any ideas?
 
1 - 2 of 2 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top