I have a 2004 ford focus zx5 with a 2.3l motor. We just had the throttle body, speed motor (?), PCV and intake exhaust cleaned all this by a independent shop, the mechanic said we needed to have the computer flashed to recalibrate to the changes he made. He couldn't do it and told us to go to Ford and have it done. Ford flashed the computer. We have had the car back about a week and the idle seems pretty fast (all the time) like around 1200 rpms while idling in gear. In fact if you are idling and take you foot off the brake the car takes off pretty good.
Looked on line and everything tells me the idle is factory set. Couple Internet articles said you could do some things with the throttle body and "trick" the computer to reset. Called ford and they told me I need to go back to the guy that did the throttle body, but seems like this is a computer control issue?
Ford told me if I brought it back they would have to hit me with another diagnostic fee!
The engine idle speed is controlled by an idle air control valve. It can be bad or dirty. And yes, the computer tells the IAC how it should be operating. As far as flashing the computer, that wasn't necessary. Has anyone checked for vacuum leaks?