rattling coming from engine?

There's a rattling coming from my engine, I think it's from my oilpan. Here's the kicker. The rattling doesn't change at all with RPMs, and it's intermittent.
edit: just realized I forgot everything important. it's a 98 4 .0 with the 231.

Noises are notoriously difficult to isolate online. I'd recommend getting your XJ up on a hoist and start snooping around. Start by inspecting your entire exhaust system including hangars, etc. Pay special attention to the catalytic converter and it's shield. They commonly start to make noise when they get old....Good Luck!

rattling in the oil pan area could be loose flex plate bolts