91 Lumina Euro rough idle

My girlfriend has a 91 Lumina Euro 3.1 with 160,000 miles on it. The car seems to drive fine but it idles kinda rough. I've done a full tune up on it and even changed the IAC module but nothing helped. It's probably no big deal but she can't afford a new car at this time and i'm trying to prolong the life of this one as long as I can. My buddy seems to think it's the intake manifold gaskets. I'm thinking it may be a fuel injector or an ignition coil. Do catalytic converters ever get plugged up? Any suggestions and/or tips on getting this car to run good and making it last a couple more years is greatly appreciated. Thanks in advance. Brian

The engine in that car doesn't have the intake gasket issues the newer ones do. I'd suspect a bad injector or coil/module/crank sensor on that model. It could also be a bad ECM due to it being mounted under the hood and exposed to the elements.

Thanks for the info. I had already bought the intake gasket kit for around $40 and it included the o-ring, valve cover gaskets, t-body gasket, and upper and lower intake gaskets along with some rtv. I would like to fix any oil leakage and clean the engine up a little bit. Her coolant looked pretty oily as well. I figured it wouldn't hurt to do this. Where is the crankshaft sensor located?

Also her engine rocks and makes a clunk when she puts the car in gear. I'm assuming a bad motor mount. I already replaced the dogbones. I found the trans mount but am still searching for the motor mount! Can anyone help me out here?

Alright, I put a new battery in the car and the thing seems to idle a lot better. Never thought it would've been that. I went ahead and changed the crank sensor anyway, big mistake. Lets just say brittle plastic and three hours later... I would advise not touching the crank sensor. Also I dropped the trans pan to put a new filter and gasket on it. Well the dealer gave me the wrong kit so I went to the parts store and they gave me the wrong one. Come to find out for some odd reason her car has a 4t60 transmission in it. I also found the motor mount which was falling apart as I touched it. That's another day another time....