1991, F150, 5.0, XLT, automatic. There is about a 6 sec delay between swipes on the fast or "regular normal intermittent" speed setting which seems to be quite long especially during a down pour. Any suggestions please. Thank you

 

ANY delay in the LOW or HIGH speeds indicates a problem with the motor. It can be changed without removing the wiper valance (the body panel between the hood & w/s), but it takes nimble fingers to get at the little clip on the end of the shaft.

If you have the newer style of motor, you can use this, but I think you have the old style.