Fast idle with on cold start

[rmunley]

Just picked up a 1991 s10 Blazer with the 4.3 v6. When I start with a cold engine I get a VERY high idle speed. By cold I mean like the first start of the day or after its been sitting for a few hours. I live in Fla and it will do it with an outside temp in the 90's. Starts fine, drives fine and no computer codes. Any idea where I should look first?

[citydriver]

How high is VERY high? Do you have a Tach? No matter what the outside air temp,the engine may idle at around 800rpm for about a min....OR you may have a bad COOLANT TEMP. SENSOR..it could just be misreading and not set a trouble code...just a guess,hope this helps

[snoman]

I would go with the bad engine/coolant tempature sensor idea too!