1991 Buick Century engine light

You need to retrieve any trouble codes associated with the check engine light coming on, and that may give you a clue what's wrong.

Get a short piece of stiff wire or a paper clip. Look under the dash below the steering wheel and find a 12-pin female plug in two horizontal rows of six. Push one end of the wire or paper clip into the upper-right-most hole and the other end in the hole just to the left of that one. Then turn the key to on (but do not crank the engine). The check engine light will flash two-digit codes. The first one will be 12 (one flash, pause, two flashes). Then there will be a longer pause and perhaps more flashed codes. Write them down. THe cycle will repeat as long as the key is on. Then look them up. Google GM and OBD1 and codes and you should find a list. https://www.2carpros.com/trouble_codes/obd2