1998 cherokee 4.0 missing at idel no stall

Hi new here.I have a 1998 jeep cherokee sport 4.0 130.000 miles.Got it last spring.When I first start it and let it idle after about a minute or two it will start missing if I rev the engine it will go away and it runs great.If it sets for 30 to 45 minutes it will do it again.I noticed a hairline chack in the exhaust down pipe by the weld and put some muffler mender on it today.Have not drove it sense. could this be the problem?

I have the same problem with my 99 Sport. Did the muffler mend make a difference?

If you've never replaced the Crankshaft Position Sensor I'd consider that possibility.

Muffler mender didn't work.I guess I'll try the cps next