Sounds like the O2 sensor to me. My car had almost the same problem, except mine never stalled, the idle would jump from about 500 to 1100 RPM's when I was stopped at a light or when parked. Sometimes it felt like it was going to stall, but it never did. Have the O2 sensor checked, it may be sticking...

~*TJ*~ 97 GL Sport Zetec
~*RIP*~Connie~*1/21/02*

~*Mods*~ E0 SVT Rims~205/55R16 Goodyear American Eagles~

~*Mods to come*~ H&R springs~Konis~Coilovers~17x7 Millie Miglia Avia~215/45R17 S-03's~SVT body kit~98+ OE Spoiler~CAI~Brullen Cat-Back~Turbo (or 2):)~

More to come