I had an intermittent problem with that sensor on my PA. When the error code in the computer was checked, it showed up as a problem. I had it replaced. The cam sensor can cause a similar problem.
check crank sensor
The 1991 Buick IAT sensor can be found in the air intake hose. The IAT sensor will be between the air box and the top of the engine.
check the MAF - Mass Air Flow Sensor
under the water pump.
It's just behind the harmonic balancer.
check the fuses then check high/low beam switch
check your timing
Check out Crutchfield.com
Sounds like it could be the Vehicle Speed Sensor (VSS), but you might check the wiring connections at the sensor which is mounted on transmission.
To replace the cam sensor on a 1991 Buick Regal with a 3.1L engine, first disconnect the negative battery terminal. Locate the cam sensor, which is typically found near the front of the engine, and unplug the electrical connector. Remove the mounting bolts and carefully take out the old sensor. Install the new sensor in the same position, secure it with the bolts, reconnect the electrical connector, and finally reconnect the battery.
On the 3.1L & 3.8L engines, the CMP sensor is located on the timing cover, behind the water pump, near the camshaft sprocket.
There are two. One by the water pump, and one down by the pully. You have to have a puuler to get tho that one.