Speedometer

Your 93 ford taurus has both a speed sensor used for your cruise control and antilock brakes system and it has a speedometer cable that operates the speedometer.If tyhe speedometer is not operating corectly the cable is suspect as is the speedometer head itself.

The speedometer cable runs from $42 to $61 at the dealer

I don't know this car specifically, but there's probably a speedometer cable and a sensor. The problem could be at either end--with the sensor or with the connection at the dash.

I recommend getting a repair manual for this car and checking the diagrams--they probably have a manual at your local library. That'll tell you whether or not you can replace the part yourself--could be a big job.