i had this problem but it was due to my o2 sensors being on for a month. (upstream and downstream) but when i replaced them, the guy who checked the codes told me to also clean the throttle body, MAF, and also the Idle control by taking out and spraying it down with carb cleaner. which is that part under the throttle body. its about 4 inches long and about 2 inches thick, has two bolts holding it in, one which is visible under the throttle body and on that is a little hard to get to. just my $.02.