97 ZJ 5.2L -- Light Rattle at Idle --Solved
 

Success!!
After hunting for a month, stethoscope in hand and replacing a few
parts , it was the water pump.
Once I had the pump off you could see it had been leaking.

I had a devil of a time getting the heater return tube to seal
properly.-- why this isn't a hose I'll never know.
I dont know if the last guy bent it or what ,
I kept ruining the o-ring. After a couple of orings we bent the tube
so it would enter the pump more squarely
and I coated the end of with some RTX gasket sealer. Now shes dry as a
bone and running very smooth.

Idle Pulley - No
Fan Clutch - No
Alternator - No
Water Pump - Yes!!

Oddly enough I could only hear this rattle after I had replaced the
MAP and TPS Sensors and got the idle right.