Another problem

today on the way home from school my car started acting up on me again. Its idling up really high (about 2k rpm in P/N). In gear it keeps trying to rev but obviously the brakes are stopping it. I am worried that i will overheat the tranny if this keeps up very long. When i got home i looked at the TB and it seemed to be fine. I didnt remove the intake to check inside, but the linkage worked fine. Has anyone else had this problem before? If so how did you fix it? thanks in advance for any help