well, heres what i was thinking. but keep in mind this is with manual trans, and i know jack about automatics. there is one idle set by a screw on the intake, and another set by the computer(and two idling modes, one when your stopped one when your moving, here i'm talking about when your moving). the computer adjust the idle by your driving habits.i know this for a fact because when my girlfriend drives my 1994(manual) she rides the clutch petal(rests her foot on the petal, clutch slips) the computer adjust the idle from my driving(1250 rpms) to hers (2000 rpms, it would be more but the computer limits the idle at 2000). then when i drive it again, some times the idle would go back down, other times i had to reset the computer. reseting the computer is easy, some people take the negitive cable off the battery, but its better to go under the hood and take out the PCM I and PCM B fuses and put them back in (both at the same time, one at a time may not work). if you do this your car may start and then die, but but the second time you'll be fine. like i said this is what i do with my car, i can't promise anything with your car.
ok, i'll stop blabing now, injectior cleanier wouldn't hurt