Idle Problem shortly after starting - Need help ASAP

[jp72]

My 2000 Buick LeSabre has over 300,000 miles and still runs beautifully - most of the time. The idiot light came on a couple weeks ago, and I found that my 5 year old battery needed to be replaced. That done, I thought the light would go off. Wrong. The car then began very strange behavior. It starts fine, but when the temp gauge hits about 60 degrees, the idle gets really rough. Usually it will chug until it dies unless given some extra gas. Once you rev the accelerator once or twice, it evens out. If it doesn't die and just chugs for awhile, it evens itself out around 80 to 110 degrees. If I try to drive it before 110, it'll lose power making it feel like the accelerator isn't working. Once it gets past this temp, it runs fine. Although my gas mileage seems a little worse than usual.

I'm suspicious that the catalytic converter might be bad. At times, there's an exhaust smell in the cab.

PLEASE HELP! If this car goes down, I have no way to go see my kids.

[polarzak]

Could be several things, but without guessing, and the Service Engine light is on, get the code read first.