check the computer module UNDER the coil.
try changing plugs and wires then move to coils. if not there it could be and o2 sensor.
Fan Relay
Try changing the CRANK SHAFT Position Sensor.
go on you tube it will give you the answer faulty scorpio speedo
map sensor
on a 90 olds 88 royale your sensor sits inside the timing cover...will need to remove the harmonic balancer (need pulley for that) and remove two screws to take sensor out. replace all parts same way they came out and in same order. passenger side of engine in timing cover
Since no year given I can only guess, check the crank sensor
The next step should be to check the oxygen sensor. If this isn't the issue then check the coil or coil pack to ensure proper firing.
Crank(or cam) Position sensor would be a good guess. It tells the engine when to fire
crank sensor or cam sensor
Wiring, computer, or engine mechanical problem.
I would start off by checking the crank shaft sensor when this sensor goes out the plugs will not fire.