There is a thread (Re: ISC troubleshooting) in the archives addressing an
idle circuit problem that gives similar uncontrolled 3000 rpm symptoms to
those you are observing.  I found heat inside the idle control unit behind
the right tail light contributed to the problem.  My experiences and
attempts at fixing this can be found in Item #394156 (21 Feb 2010 18:13) -
Re: ISC troubleshooting.  Sometimes electric motors begin to draw more
current as they age.  Maybe the idle control valve is doing the same thing
and causing the control circuit to overheat.
Ed