'87 5KCSTQ Idling Problem

[Rob Silcher <rsilcher@mc4adm.UWaterloo.ca>]

I'm driving home at lunch, the car isn't hot yet - I come to a stop light 
and instead of idling at 900 rpm its running at 2800 rpm.  I get home 
- open the hood, play with the throttle - its not stuck.  It eventually 
goes down to 1000 rpm but kind of rough - sort of bouncing up and down.

If I give it a shot of gas it goes way back up to 2800 -3000 rpm.

I'm new to this car - what are the obvious places to look?  The manual 
suggests the warm-up valve (I'll test that with my ohm meter). Any other 
obvious ideas?  The temp guauge is working kind of intermittently but the 
fan does come on when it gets hot. I'll clean the electrical contacts but 
I doubt that is the cause.

Thanks in advance,

-Rob Silcher