94 LX T-bird Rough Idle
So I'm sure this is a common problem in older cars but any input would be greatly appreciated. My car has a terrible idle at stops. It seems to be random like sometimes it will be the first time i'm running the car for the day and it will run great for 5 minutes then start idling rough then pick up again and be fine. Then other days it will run shitty right off the bat. This has been going on for a month or so and it rarely full blown stalls. I'd say maybe 4 times over the past month its actually stalled. Most of the time it drops to like 300-400 RPM's Then shoots back up and back down again to eventually level out where it should. I've heard maybe spark plugs, vacuums or IAC . By the way I described its acting is there anything any of you guys could point to as most likely being the issue. I would just take it into the shop but I just got a $600 bill from replacing the catalytic converter and want to try to fix this one on my own. Thanks in advance.