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Idle Problem

My 89 Caddi DeVille is idleing extremely high, and is nearly impossible to drive. My only guess to this problem is the idle control valve/switch. What else could it be? Or is my guess most likely the soloution…

Other possible problems are vacuum leaks, excessive carbon in the throttle body, or a sticking throttle cable. I would first make sure the throttle plate is closing fully and nothing is obstructing it from doing so, and to check for vacuum leaks. These are cheap, simple things to check. You may also try removing and cleaning the IAC before replacement if you get to that point.

Let us start with mileage, basic maintenance that has been done, plugs, plug wires, air and gas filter , distributor cap, as a start. Miles since repairs stated previously and any correlating work, or coincedences as to when it started having a problem?