You should probably check your exhaust header, too. They are notorious for cracking on our rides, and the crack happens right were you are describing, and is often responsible for a nice ticking noise when the Jeep is warming up.

Get an inspection mirror and a flashlight and crawl under your jeep when it's cold. Right on the collector where the header is bolted to the exhaust pipe, where the two pipes of the header meet, use the mirror to see if there is a crack on one of those two pipes on the top part of it.

Just replaced mine, had a pretty hefty crack in it. Ticking noise...terminated.

 

i just got my jeep back driveing today after installing a 99+ intake 703 injectors stainless header and a home ported tb and when i started it up there was a slight tapping sound i started looking at things and at first found nothing. I went inside and was getting more and more mad that i just did all of this work and now something is wrong so i went back outside and took off the belt and spun the water pump pulley by hand when i noticed the inside of the pulley was contacting one of the water pump bolts so i removed the pulley and discovered that the pulley had a slight bend at the outer edge so i got the trusty hammer out and worked it back to its origional shape. I was carefull takeing everything apart and didnt drop it so the only thing i can think of is it has been like this since i got the jeep and when i installed the new pump the head of the bolt was in a diff position than it was prior to the install so u might want to check your pulley

 

I got the same loud tapping noise in my 2000 Cherokee 4 liter six. Very loud, and similar to a collapsed lifer or con rod with that same staccato/ metallic sound.
However other factors say its something else:
Oil pressure is good--hot idle >30, hot at speed >50 PSI
I have listened to various parts of the engine--the oil pan is quiet, the front of the engine is quiet, I even inserted a tube into the oil filler to listen to the valves/ rockers--quiet--almost turbine-like quiet.
However, when I put the tubing at the firewall, above the bell housing--bingo--loud sharp noise.
I pulled the inspection plate off and tightened all the TC-to flex plate bolts--all were as tight as when I installed this engine 30,000 miles ago. No evidence of any bolt heads hitting anything in that area--no bright marks or scratches.
The character of the noise changes, unpredictably, sometimes it is almost gone. Other times there is a hollowness to the sound; not the solid noise I hear most of the time. Oil pressure shows no fluctuations. Nothing I can see varies with the sound.
Any ideas would be appreciated before I get stranded. Company vehicle--company says to drive it until it breaks..

 

Check the exhaust manifold for cracks sometimes they sound like a lifter pecking.

 

...and how about that Purge Solenoid? Now there's a good source of ticking sounds!

It's mounted near the firewall on the passenger side.

 

Would the purge solenoid vary with engine RPM? Would it be loud enough to be heard 30-40 feet away?

 

I just pulled the engine out of my 92, oil pressure was getting pretty low and it's just worn out. Anyway, about 30k ago it started making this noise that sounds like popcorn in the crank case, I wrote it off as heat related. Now with the engine out I can turn it over by the crank and it still makes the same noise. I'll be pulling it apart soon to inspect.

 

I think the popcorn noise is a different critter. No way I would describe this as "popcorn", more like hitting a plate of 1/4 inch steel with a 16 oz hammer

 

Mine as a slight ticking too, it is a 2000. I think mine may be the injectors. It ticks at idle but when I give it gas it goes away.