Toyota Repair: Idle adjustment, air control valve, excessive vibration

Question
I have a 95 Toyota Tacoma the idles at about 500 rpm when in drive and stopped at a traffic light which causes excessive vibration.  Can I adjust the idle?  If so, how?

Answer
The idle is not adjustable, it's controlled by the computer, most of the time this is caused by either excessive carbon inside the throttle body and/or a sticking idle air control valve, the solution is to remove the throttle body and then the IAC valve and clean all the carbon deposits out of both, this usually restores the idle to normal.