Near the engine intake, you will find the idle air valve. Find it. Make sure you have found the right air valve otherwise you can destroy the whole engine by doing something with something that is not supposed to be done.
Get a screwdriver. Remove the electrical plug on the back of the idle air control valve with a screwdriver. However, be careful about the plastic tang that is holding the wiring harness. Do not destroy it or break it apart because it the wiring to the harness will split apart and that will cost you a lot more than cleaning the air-valve from a mechanic. The wiring harness is kept from vibrating off with the help of that plastic tang.
Detach the screws of bolts that are occupying the idle air-control valve. Hold the valve pointed downward, and spray the pointed end of the valve with carburettor cleaner, and wipe it clean. Continue the process until the carbon is removed completely from the air-valve.
When the carbon is removed completely, the air-valve should be placed back from where it was detached and attach the wiring harness to its old location.
Check the cleanliness by starting the car. If it idles perfectly and drives smoothly then the mission is accomplished otherwise you will have to open everything again and repeat the above steps. If you can’t get rid of the carbon, you will have to buy a new air-valve.