Our 91 Buick Century just started quitting sporadically and now pretty much doesn't want to run. The service engine soon light is also on. It is a V6, automatic. Really don't have any idea where to start looking. It might be fuel, electrical, etc. What would be the best direction to start looking, or any ideas.

Since the Service Engine light is on, have you pulled any codes?

With the SES light on, you will have a stored code.
Probably the best place to start with an OBD1 vehicle is to read the stored code/*.
Here is the paper clip code test....
https://www.gmforum.com/obd-i-troubl...p-test-306836/

& here is the listing of the OBD1 codes:
https://www.gmforum.com/obd-i-troubl...eneric-306838/

Yes, code(*) . . . and:

How many miles on it?

How long have you owned it?

Any recent work done on it?

How many miles on the spark plugs?

How many miles on the wires?

How many miles on the cap and rotor?

Is the air filter in good condition?

What area does it live in?

There are any number of things that my cause the problem......

Could you be a little more specific?

Does the car start and run ok, first thing in the morning?

Does it have a starting problem when it is warm?

When driving on the highway, does it misfire going up a slight grade when lightly accelerating? Does it feel like a misfire problem?

You say the CE light is on.....is it on while the vehicle is running, or are you talking about it comes on when the vehicle stalls/dies?

Did this just happen or is it an ongoing problem?

This is a 3300 engine which is famous for what "seems" like, a slightly rough idle.......it has three coils that sit on an ignition module....one at a time pull the ignition wires of each coil terminal and look for corrosion/carbonning on the metal terminals of the coils....

Has the battery recently been disconnected or replaced? If yes, and your problem is stalling, it could need an "idle learn" procedure.....

The guys and moi have asked you a lot of questions, and it would help us to diagnose the problem if you could answer them.....the simplest answer could be a complete tuneup, if not done in awhile(plugs, wires, air and fuel filters, PCV valve, cleaning of the throttle plate and bore, and IAC pintle and passageway)......

The code is 34. There is a difference of opinion whether this car even has a MAP sensor. If it does where it is located. The ignition module was replaced this week and 2 small vacuum hoses that were cracking. Otherwise no repair has been done recently. Car has 129k. Has been serviced, etc. on regular basis. This problem came out of nowhere.

Funny thing about OBD 1, is that the codes can mean different things vehicle to vehicle.

For example, much of the internet cites code 34 as a MAP issue.

This site does not:
https://www.troublecodes.net/gm/89-91_33n_mfi/
Rockauto parts listings also favor a MAF based setup.

If this is MAF related, typically if the MAF sensor is unplugged, it will force the computer to fall back on default air/fuel tables. It won't run/idle perfect, but if it behaves differently than before (usually for the better), it'* usually a confirmation of the code, and usually points to either a bad MAF sensor, or wiring issue.

Also, if the issue is a broken MAF sensor, it can typically be confirmed by tapping the MAF at idle while the sensor is plugged in, usually with the handle of a screwdriver. If the car changes behavior (stalls, etc), it'* the issue.