I have noticed that at idle, the power steering assist is minimal. Increase the RPMs and the assist improves. Where this becomes a problem is on curves when I increase or decrease acceleration, as the...
I would call a Ford truck dealer shop. This could be a serious issue. Another thought, air in the system. Could try to look up how to purge steering system. On some systems, you need to remove weight from the front end, turn steering wheel all the way to one direction and hold. Then turn the wheel all the way the other dierction and hold. Bleeding Verify that you have or have not electric steering!