Vac leak, air in your coolant, or a bad IACV would be my top 3 guesses. Other than that, it could also be an electrical problem, but unless your headlights are dimming or you're experiencing some other electrical problems, I would focus on the first 3 things I mentioned. Check all your vac hoses, ALL OF THEM. Sometimes there's one on the back of the intake manifold which you may have forgotten about. If all the Vac hoses are accounted for, and are not leaking, move on to your coolant. Bleed your coolant by running the car with the radiator cap on loosely with the heater blasting full-hot for at least five minutes(preferrably until the engine starts to come up to operating temp), and then shut the car off and top off the coolant if needed. Repeat the process and put the cap on tight. Now check your idle again. If it still fluctuates, then try letting the car run with the IACV disconnected. With the IACV unplugged, your idle should drop to whatever your idle adjuster screw is set at. If it does, and stays constant with the IACV unplugged, your IACV is probably toast. You can try taking it off and cleaning out the little mesh filter and see if that helps. If it doesn't, look for another IACV. I have an extra OBD-II, but I don't think it'll work with your setup.