odb I or II?

is it completly random?
or have you just not figured out a pattern?

only when cold? only when warmed up?
stop and go traffic?
only on the highway stead state?

if you can reproduce it and you aren't getting inspected anytime soon, if it is the o2 sensor as sugguested, you could unplug it. the first one, not the second and see if it clears up.

it should put the jeep in a limp mode and richen it up so don't run it like that for long.