There's been so many posts on this topic i decided to do a tutorial thing on it. Its not difficult to clean the throttle body, almost anyone can do this. If you can change your own oil you can clean your own throttle body on your own engine.
The usual indication you need to clean the TBI is when the engine idles rough or even stalls. The TBI butterfly and IAC (idle air control valve) get dirty after many miles because they are bathed in oil vapor courtesy of the PCV valve, which is routed directly into the plenum and then migrates onto the TBI and IAC causing dirt to build up on these parts. And this dirt can ultimately affect the butterfly valve (holding it open too far just a tiny bit but enough to affect idle) and the IAC (causing crud build up inside that affects the air/fuel ratio at idle). Fortunately it is quick, easy and cheap to remedy this situation and all you need is a phillips screwdriver and a can of your throttle body cleaner of choice.
Photos are directly below captions from here on.
1. All you need to clean your throttle body, old toothbrush is nice to have here but not essential, you can do it with rags or paper towels if that's all you have. The Sea Foam Deep Creep is a good product and said to be safe for the I.A.C.
: I've read posts from other people that killed their IAC valve using other products such as throttle body cleaner, so use a comparable TBI cleaner or carb cleaner only if that's all you can get at the moment.
2. Loosen the big hose clamp as shown. (Usually there's no need to remove any of the other hose clamps or hoses in this area, just the big one on the air filter hose where it mates with the end of the plenum.) Then pull the end of the tubing away from the plenum and push it down slightly so the throttle body and butterfly are exposed.
3. Now wedge the throttle open with a big screwdriver or something as shown. (Thanks Mike G for the good tip)
4. Clean the throttle body throat and both sides of the butterfly valve with the spray can cleaner, rags and the toothbrush. Its best to spray and wipe the dirt away along with excess cleaner.
The hole shown goes to the idle air control valve. This valve controls the air allowed into the engine at warm up time when the engine is cold. And as about a hundred posts on this site prove, the IAC can cause you a lot of trouble if it is allowed to get too dirty. But there's usually no need to remove the IAC just for cleaning; just soak it but good through its hole and this will dissolve much of the crud that can make it malfunction.
5. When it is clean enough for you, look it all over and make sure there's no tools left inside the Throttle body and then put everything back together.
The first time you start the engine after doing all this, bear in mind that there are going to be huge clouds of smoke coming out your tail pipe for a couple of minutes. And while it looks a little alarming it won't hurt the car, so don't worry about that. I run the engine at about 2,000 rpm until the smoke starts to subside and i dont try to drive it off! Because i dont want to attract the attention of the police or anything like that. If the area you live is particularly sensitive about smoke coming out of your tailpipe, then maybe i'd wait until late at night to restart the engine when the smoke will not be so obvious.