Nissan Repair: Nissan NX 1991 only runs well with cooling fans on, nissan nx, car idles

Question
So the problem is this:  The car starts when cold and idles great.  After a few minutes the engine won't respond to very slight throttle - it will stall right away and I will have to wait 30 minutes before it will start agin - like it's flooded.  I can hear that it's going to happen because the car idles up a bit.  Now the strange part is - Ocassionaly, while I was trobleshooting, the cooling fan would come on and the car would run perfect and respond to light throttle - cooling fans shut off, engine stalls with light throttle.  

Here is what I have checked according to the shop manual and ohm meter with good results:

IACV regulator has voltage and proper ohms
TPS has proper ohms
Idle up solonoid is clean and clicks with voltage.  
The idle air adjusting unit is cleaned and has voltage and proper ohms.

My question is this:  why would the engine operate normally when the fans come on, and not when they are off?  It's driving me crazy.

Thanks for your expert advice

Capt. Jeff Duncan
Dennisport, MA

Answer
My thoughts has to do with the temperature sensor that is signaling to the fans to turn on and off.  I think it is stuck in cold mode due to a defective temperature sensor.  Remember that the car is old enough to use multiple sensors.  One is for the gauge and one is for the fans and computer.  Basically, when it is simulating choke mode it runs well.  After it warms up the thing runs bad.  It sounds like it is in cold start mode.