high idle and missing on 2004 Jeep Grand Cherokee

my jeep will rev high to 2rpm when first starting it up. i turn it off and restart and it acts normal. it has been known a few times to rev high while in park. so i shut it off and back on and it does fine. also when driving the rpms will fluncutate up and down and the engine feels like its missing. i have replaced the idle sensor. it still does it. the check engine light doesnt come on. im at wits end! please help.

Asked by for the 2004 Jeep Grand Cherokee
Try diagnosing the problem with a scantool you may have a pending code, i would also check to see if you have any lines broken from the air inlet