Irregular idle 91 Acura Integra .

Hi all .
Hoping someone has had this problem and can help diagnose .
1991 Integra LS . Street car with header and cold air intake .
Irregular idle , idles up and down between I think +or- 750 and 1000 RPM just after start up when engine starts to warm up . This will continue even when the engine is up to full operating temp for longer than 15 minutes . More in particular the ambient temp today was about 25 deg's
I was thinking temp sensor . But I'm not sure where to look for it .
The thing that leads me to believe it is a temp sensor is that the cooling fan runs continuosly untill the battery is dead .
Thanks .

Does the engine rev fine, or stop at ~3000 RPM? I am guessing the problem is the Throttle Position Sensor (TPS).