I'm affraid this has an expensive answer...

The PO of our '87 GL (2WD) apparently unplugged the idle speed ctrl valve.
I can't feel any vibration but haven't put the ohm meter to it yet. Plugged
it in, started up, and the engine rpm shot up till I shut it down (quickly).

Since I replaced the O2 sensor she idles evenly with the valve unplugged
(although a little high.) and generally runs very well.

The Question...
Would leaving it unplugged (thus deffering an expensive replacement) cause
any ill effects?

--Chris Arnold
  '87 GL
  '86 honda (239k mi)