If its a new install, let it warm up to operating temp and take it out for a test drive.
It's common for it to idle high for a few minutes, plus the ecm will learn,log to the driving habits, then should stabilize after a few miles.
Actually there is a procedure just turning the screw wont do any thing. Idle Air Control
Torx bit # T-20
Take the paper clip and open it up and form it into a big "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' pins.
Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.
Start engine. You are now going to adjust "minimum air". There is a Torx screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.
Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).
If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait 5 minutes. This will clear the ECM of all trouble codes. Re-connect the battery and drive the car for 20 minutes to allow the ECM to relearn your driving style.
Mine idles high, around 1K until the engine gets warmed up, then it sits around 700, if not a little lower. I was running at around 650, but have been having issues lately with it dying on me when driving. The idle would drop really low when letting off the throttle. I upped the idle a little and that seems to have helped. I just adjusted the idle the other night. gmakra has the correct process, but forgot one step. When you adjust the idle screw you are actually manually setting where the throttle linkage sits. As a result, your throttle position sensor (TPS) will be off. It is just a POT that relays where the throttle is to the EMC that helps to control fuel on sudden acceleration changes.
To adjust: Connect up a volt meter positive to the blue wire, ground to black, and measure the voltage when key is in the run position. You should be right around 0.50 V If you are not, you can loosen the screws on the TPS and rotate it some to get the voltage you need. You may have to take it off and wallow out the holes a bit to give you some wiggle room. Rotate it and tighten it back up. Make sure you dont leave the key in the 'run' position too long or you risk burning up the ICM. Best to just unplug it and not worry about it while working.
Also the picture 1986cj put up has the plug that is difficult to remove. If you have that one, grind it flat then drill a hole in it to access the screw.
Colorado Jeep Club Member #2086