my 1990 buick century is souttering real bad while driving and now when i start it it wont idle it cuts off like theres junk in the fuel line or something what could it be

Bad spark plug. Bad wires. Bad rotor & distributor. Bad fuel injector. Bad wiring to injector. Dirty IAC if it has one. Dirty carburetor/throttle body whichever it has. Too much carbon build up in engine. Bad gas. Clogged air filter or gas filter. EGR valve. Low fuel pressure. Compression issue. I know this probably doesn't help but it could almost be anything. You have to eliminate each of these by testing each system. Air/gas/fuel then mechanical

Some suggestions: I did have running problems and the fix was, I replaced the engine coolant temp sender brass 2 wire like probe. This was a very easy part change and the engine runs better and better mpg. Because I read this was a common problem with these engines and because the computers are simple and their is no temp gauge on the dash, there's no indication it's not sending the right temp to the computer. So the computer thinks the engine is cold etc and adjusts the fuel wrong etc. The sender just unscrews with a deep socket and the sender is hard to see but you can follow the wires and feel it's just under the top of the serpentine belt area on the passenger side of the engine. Coolant will start leaking out when removed and don't over tight the replacement. Ebay had the cheapest price for me was under $15. Take care Also there is a battery power cable inline quick disconnect connector for easy power off resetting the computer for mechanics, just after the battery terminals what was green corroded inside when disconnected, corroded from the nearby battery off gases.This was causing the Buick's power to completely shut off the whole car when driving. The connection terminals were so bad I had to just cut the ends off and add permanent crimp connectors. Also check your engine wiring harnesses to sensors etc especially that run between the serpentine belt and look for any frayed wire insulation or missing plastic conduit loom from years of heat and grease. Repair any damage with electric tape and new loom as exposure may be effecting signals to computer. Sign into a Buick car forum and post your question, lots of helpful Buick experts there. Take care