Low At Idle In All Ranges
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2002 Lincoln Navigator, 2002 Ford Expedition, 2001 Lincoln Navigator, 2001 Ford RV Cutaway, and 2001 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
Check for low fluid level, restricted inlet filter, loose main control valve body, solenoid body or accumulator body-to-case bolts. Excessive leakage in pump, case control bodies, sticking main regulator valve or damaged inlet tube seal, gaskets or valve body separator plate.