Help with Idle Problem...?

[corylang@dccnet.com (Cory Langford)]

well,

Here is the scenario:

It is getting a tad bit colder around here (and a whole lot wetter).  Car
runs fine when it is under load.  Idles fine when sitting.  Starts fine.
BUT, when I let the car rev down on its own (say when you are approaching a
stop light and simply put the clutch in and let the engine slow down while
you coast), the revs will go way to far down. 

started just dropping momentarily and then settling in at 1K nice and
smooth.  It has been getting slowly worse until now it drops too low and
stalls.  If I slow it down and drop the idle from about 1.5K no problems,
but from 2+ K it will stall when you let it slow with out feathering the
gas momentarily. You only need to do it once and then it idles great. Takes
off great, etc.

It is straight CIS (not E) 8V

Any suggestions on where to start to look?

Not sure if it is weather related, but it never did this during the summer.

TIA

Cory