idle surge

i have a mx6 '92 with 4 cyl. engine that does not idle properly when cold (cold weather).... will start fine but idle increases to about 2500 rpm, then suddenly as if the power was cut the idle falls back to around 750 and increases again to 2500 to go thru the cycle again... the duration between cycles is about 8 seconds... once the engine warms up the idle speed remains normal... where do i begin, i can replace parts but have no test equipment...

My car does the same thing, I am not sure what it is, but if you go to consumerreports.com and you enter in the search for a 1990 mazda mx6 it states that one of the problems for the generation is that it has a bad coolant sensor that causes "surging" when it is cold. As well as water leakage in the trunk and other things. Hope this helps