Re: 2002 TJ \"swishing\" noise from 4.0
Loosen the idler pulley and see if it effects the "event". ...or even remove the belt and start it up and see if it still occurs. This is something with a varied load/imbalance/??? so this should effect the event if it has anything with the rotating masses in the front of the engine. Naturally you can't do this for long and it will probably upset your computer temporarily.
Simlar noises (guessing) ...loose flexplate bolts (requires an automatic and sounds somewhat like a rattling weather cap on a large diesel) ..but that would not vary much except when you put it in gear ..where it typically stops.
Please post what you eventually find out. I'm sorry that you're going through this [img]images/graemlins/frown.gif[/img] ...but I love these puzzles [img]images/graemlins/grin.gif[/img]