I have a 94 f150 that I recently cleaned the throttle body on. Ever since then, when I use the cruise control it surges up and down by approx. 5mph. When I turn it off and just use the pedal it is fine and does not surge. The cruise control is not vacuum operated it is run off the rearend speed sensor. Any thoughts? The speed sensor was replaced about a year ago.

The cleaing itself cannot be the cause, but it is possible that the cruise cable is binding because it was removed or it's placement was altered. Check for any binding or crimps in the cable.

I didn't move or remove any cabling at all, does anyone have any test diagrams or checks that can be performed to isolate this? Maybe the amplifier assy went south?