when i crank up sometimes...

my rpm's go up to a 2.. then back down to a 1.. then up to a 2 again.. etc etc

the engine rev's up like that until i hit the gas petal or either put it into gear and drive. but it will stop if i do either or.

it also happens sometimes when im going somewhere and then pull to a stop and put it in park.

anyone had this happen before and know what to do about it?

what year is it?
might be a t.p.s. problem
i'm new to these jeeps, but most injected motors have throttle position sensors and whatnots. i will ask some of my shop guys and get back 2 u