Still pluggin away on this project with my 16yr old son. His first car if we can get it running a bit better. The idle is quite high--replaced the air valve on top of the cam cover and that helped some. Can't seem to find any air valve knob(the black one under the intake manifold) how do i throttle this thing down?

Matt -

The IAC is the gadget that allows some air into the engine when the throttle is closed. Test it with a large pair of pliers. With the engine running close off the nearest hose connected to the IAC. If the idle drops, well... The IAC isn't working, either it's kaput or the electric signals to it are MIA or incorrect. Disconnect the harness and check across all terminal pairs with an ohmeter. None should read open. If yes, new IAC. A used valve must match all numbers, Manual trans not same as automatic. Same unit p/n for your B23 and the 1982 and older B21 engines. Sometimes the motor part gets stuck from sitting unused. light hammer taps helps. (Percussive Maintenance)

With the engine off, turn the throttle slowly open and listen for a click when the throttle position switch trips. Check with Voltmeter to be sure.

Good Luck,

Bob

Sounds like a bad idle air control valve. I believe it is located right behind the distributor. Did you happen to catch the "click and clack" brothers on NPR last Saturday? Someone called in with an '87 240 with an idle that was so high that when they stopped at a light, it bucked and they hit the car in front of them!! One of the brothers brought up an interesting point. Said years ago a customer had a 240 in for a high idle, the idle air control valve was bad, and it fried the computer. Said he didn't know it fried the computer, so he swapped out another 240's computer that was in the shop. Well, the bad IAC valve fried his other customer's computer as well! Guess he didn't make much money that day. Live and learn I suppose.

Anyway, I think the Idle Air Control Valve is quite easy to replace. Good luck.