Engine RPM Limiter
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2007 Ford RV Cutaway, 2007 Ford Pickup, 2007 Ford F550 Super Duty, 2007 Ford F450 Super Duty, and 2007 Ford Econoline. However, it is still accessible from the selected car via links, so may be relevant.
The PCM limits the engine RPM by cutting off fuel whenever the engine RPM limit is detected. The RPM limit for the F-Super Duty and E-Series is 4,000 RPM. The purpose of the engine RPM limiter is to prevent damage to the powertrain.