High idle revs in cold weather
 

Hi all.

I have a 92 Tracker, and since the really cold weather arrived a few
weeks ago, it has been revving very high (around 2500 RPM as opposed
to around 1000 RPM usually) when I first start the vehicle. The high
revs continues for some time afterwards, the colder it is the longer
it seems to last. Any ideas as to why and how I can correct it?

I have also found my gas mileage has dropped significantly (around 15%
less than I got before the cold snap) in the same period .

What could cause this to happen?
Could the two be related?
Any help greatly appreciated

Ian