Isuzu I-Mark Cold Start Problems

I've got a 1988 Isuzu I-Mark that has a cold weather starting problem.
When it's cold outside, it will start up with a really fast idle (2000 RPM)
for about 3 - 5 seconds, slow down to about 1500 rpm's for a while (10 seconds perhaps) then start bouncing down to around 500-600 RPMS, almost stalling, then back up to around 1200-1500 RPM's, and repeat this process maybe 10 - 20 times before the engine seems to find a good place to idle at. When the car is warmed up, the idle is rock solid at around 900 RPM's.
Last week, on a really cold morning, it would not start at all. The starter would turn, the engine would start for about 1 second then sputter out and die right away. After about 2 -3 hours later, it started like normal (normal with the jumpy RPM's).
I'm thinking engine coolant temp sensor... can anyone please help me?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.