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.
- Thanks to Ron Mitchell
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.
- Thanks to Ron Mitchell
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