i know this may not help at all, but it sounds like something electrical. cuz if it starts fine....shouldnt be the engine. but after it stalls/sputters whatever, does it drive fine? cuz im guessing that may rule out the tranny... and is the engine still warm after u come back an hour later? or is it totally cooled off? oh and does this all happen when the a/c is on? cuz my rpm's drop WAY low sometimes when i start the car w/ the a/c on.