Water/coolant Temp Sensor

Any of you all ever had problems with the water temp sensor ( or it may be caled the coolant temp sensor)??? I think I have one that acting up an a 90 model B2600I.
Thanks

Sticking thermostats could do the same thing. A worn out fan clutch could cause it to get hot while idling.

Well I never thought about the thermostat. It's not running hot but it does not want to start on a cool morning. If it gets warm and the sensor is plugged in, it may start to run a little rough and it will blow a little smoke when you hit the peadal and you can smell fuel. I assume it's running "rich" when this happens. Just looking for options. The other weird thing is that the coolant temp sensor that the auto parts store shows for the truck dies not match what is in the truck now but the plug on the wiring harness would not fit anyway. So I dont know what this mean. The one that matches in the computer is for a 93 model I beleive.
Thanks for any info.
Eric