Hi.  My '87 has had a problem during the last year in which it usually
won't idle at all until it's a bit warm.  Once the engine is warm though,
it usually idles, and the idle is smooth.  The engine always runs well
otherwise.

I had the opportunity to try switching a couple of parts from an '86
recently, and now I have a new problem.  I exchanged the idle stabilizer
control unit (behind the tail light), and nothing changed, so I put the
original back in.  Then, I exchanged the idle stabilizer valve itself.
Now, it idles when cold, but after driving even a little, I notice the
idle speed going up and down in a regular fashion every couple of
seconds. It doesn't go up a lot, but it's noticeable and new.  This is
all with the AC off.  When the AC is turned on, the idle speed comes up a
bit, and there seems to be less fluctuation though I still notice a
tiny bit of the up and down.

So, I seem to have created one problem while solving another, but I
suspect that they are related.  I know the surging idle issue has been
discussed before, but I didn't pay close attention to the discussion. In
addition, i'm not sure if what I'm describing is surging.  The speed goes
up and down, but it's actually a little hard to hear while sitting in the
front seat with all the windows closed.  Some people have described a
kind of surging with much greater variation in engine speed.

Anyway, I'd appreciate any thoughts any of you may have on this.  It
seems to me that either the idle stabilizer valve from the '86 has a
different problem than my old one and/or another component (perhaps the
idle stabilizer control unit) of mine isn't working properly either.

Thanks,
david