This my sound to easy but the same thing happen to me . 04 5.4, its the same feeling. took it to the car wash opened the hood an directed the spray on the steering shaft that connects to the [rack an pinion] where the UJOINTS are top an bottom. an my power steering came back!!! the only thing it could have been dirt an ice ...got home took a can of garage door lube sprayed the two jouints. its been TWO MONTHS..works great..