My son's 93 has an extremely low idle. Upon start up, even after sitting overnight it is idling at 400 rpm. It never idles higher at start up. I've been checking around and doing searches, and it seems to be the IAC valve. Is this the case? If so, how much will I be looking at to replace it at a shop. My hands are way too big to fit all the way down back there by the throttle body.

Well is it a problem? By that I mean is the idle so low that the car wont run right at idle?

Im thinking the tach is off.

If it is the IAC, it's going to be a challenge to replace it with the upper intake still on the engine.

When I had some trouble with mine, I removed the throttle body, and sprayed some Valvoline brand carb, choke & throttle body cleaner in the IAC air passage. My idle went back to normal after that.

Cleaning can be "ok" but replacement is best. Also try to use a throttle body cleaner, not a carb cleaner as it can remove the film form the throttle body.

I had to replace the IAC and the TPS. We are golden now.

glad to hear that the issue w/ your son's car has been resolved. thanks for the update!