91 mercury sable. 148,000 miles. For some time now the car starts to hop around, like back & forth, when at about 35 miles an hour. Lately it has began to hop at any speed it is steadily running at. If i eccelorate it stops, or if i let off the gas completely it stops. What could causing this hopping around? It has been running fine besides that. It has been drive intown only for the past 3 years or so at speeds of under 50 mph, until i got it, and now is driven on the hyway frequently.

The windshield wipers also have a problem. When the squirters are used, the wipers wont shut off untill the car is turned off.