crazy idle.......

ok ive had this problem for a while on my 96 talon esi 5spd hoping it would just go away like it appeared...but seems to be getting worst.. ok i crank the car and it idles fine, but go to driving the car runs perfect but when i come to light it idles at 2k rpms and as i drive the car more and come to more lights the idle sticks to bout 3k rpms enev if i give it gas a lil hoping it would go down it just remains there..i have no check light or anything. how would i figure this problem out without a check light....would it be a bad sensor even tho theres no check light?? if anyone could help with this annoying prob please be free..

thank you ....mike