beleive it or not my car did this and was none of the aforementioned reasons, my throttle cable was to short giving false info to the dashpot, couple turns counter clockwise and done,

 

it the tps on the throttle body

 

Okay, it could be the MAP sensor or something similar, but most likely it isn't. The most common thing that causes this problem is the IAC (idle air control) valve located on the back of the intake. Those things can be a pain in the ***. My car was jumping from 1000 to 2000 and it was pissing me off, but that could be the issue.