i have an 01 sport i6 4wd with 150,000 miles. i cant figure out why my ac pump kicks on for a few seconds and off repeatedly while the engine is running i think it might have something to do with when i baught it, it had some pretty bad gunky crap in the radiator, i emptied it out and put some flush in for about 100 miles, then emptied again and but a new radiator in. the truck still overheats and starts misfiring bad when it does.
i can drive it untill it overheats, then when i shut the engine off and start it back up a few min later the temp will be even higher than before and it will misfire bad, but after letting it run for about 30sec the temp will go all the way back down quick and the engine will run normal untill i get too a long red light or traffic jam, then it will overheat again

 

Did you change the thermostat and is your fan clutch working good ? and is your e fan working ?

 

x2 on getting the answers to these important questions.

 

Is the defroster running when the AC pump kicks on?

The overheating is a separate issue

 

i did change the thermostat when i changed the radiator and put a brand new fan clutch on.
another weird thing is that the electric fan only kicks on when i turn the ac on if my switch isnt on ac the e fan will never turn on no matter how hot it gets

 

i didnt really pay attention to that but im going to go check it right now it could be possible that it only does it when the defrost is on

 

The A/C will kick on when the defroster is on, this is normal and will trigger the e-fan.
The other condition that causes the e-fan to kick on is the temperature at the t-stat housing exceeding 217-222F.

Considering your description of the problem - I would start by checking the Coolant Temp sensor (plugged into t-stat housing). First, when you pull the plug with the engine running, the e-fan should kick on. Next, grab your multi-meter and test the sensor.

http://www.fixjeeps.com/coolant-temperature-sensor.html