Do not in any way jump to the conclusion that you need to rebuild your engine as the 3.8 liter engine (and its virtually identical 3.3 sibling) are well known for being able to deliver hundreds of thousands of miles with just regular maintenance.
Originally Posted by Don Carlitos
As for your rattle, there are several ways in which you might diagnose the noise including the garden hose method (although you might have to figure out how rig it so that you can listen while you drive) or find a garage that has those new radio transmitter listening devices that they can stick all over the engine compartment to isolate the location of a noise. Your problem could be as simple as resonance in the exhaust system, a bad motor mount or any number of other relatively inexpensive to fix problems.
Sold: 1998 DGC Sport 3.8 (Final odo: 178,000 miles)
Sold: 1998 Chrysler T&C LXi 3.8 (Final odo: 190,000 miles)
Sold: 2003 DGC ES 3.8 (Final odo: 172,000 miles)
1999 Chrysler T&C Limited 3.8 (Current odo: 200,000+ miles)
2001 Honda Accord EX-L V6 (4-Speed automatic)
2012 VW GTI (6-Speed manual)