had this happen with my old cavalier, when i replaced the windshield wiper motor, one day in shop at highschool the teacher said that it was out of time, or something like that because they parked where they were suppose to when you turn them off but when i had them on they always stopped about 4 or 5 inches up and then always went to far when wiping... i don't really know how a windshield wiper motor can be out of time tho...? i never grasped that concept