My cousin has an 2000 Buick Park Ave with like 120k miles. Problem is that when youre driving it just randomly stalls out. Its only just started happening and im not sure what could be causing this. any suggestions? whats step 1?

 

If it were my car I would start with a tune up. How old are the plugs, wires*nd pcv valve. How does the air filter look? Replace the fuel filter. I would also check to see if there are any fault codes stored in the computer. The next thing I would check is fuel pressure. You may have a fuel pump that is failing. It could be a bad sensor as well. I hope this is helpful.

 

I would look into the MAF and IAC

 

Chibi and MouseHouse have great ideas to look into.

If possible, have the car scanned. I've used a Snap On scanner before that can tell me codes that have not yet reached a point of tripping the Check Engine light (this can be quite helpful).

At 120K, plugs, wires, fuel/air filter are just good maintenance to do PERIOD! For the little cost of parts and time, I would do it regardless. Chibi knows more then I do, but the MAF on the 3800s is flaky (heck, he carries the MAF cleaner in his car as part of his "just in case" supplies). Get a can of MAF cleaner and follow the directions, again, just good measure.

I've only seen an IAC on all the cars I've messed with go bad once.... But there is ALWAYS a first. But, I have seen the port the IAC works with get gummed up with crap/carbon. Might be worth a couple moments of time to pop it out and clean that area (some paper towels and spray carb cleaner).

 

Rarely, bad CAT. Above post are on point aswell.