so i have a 99 4.0. i have what feels like a misfire only at idle. i can see the rpm needle move just slightly bot not all the time. i can feel it all the time though but again only at idle. ive replaced the spark plugs with champions, wires, cap and rotor. am i looking at a bad injector possibly? also the check engine light is not on and hasnt gone on at all.........yes the bulb does work

Unplug spark plug wires from the distributor while it's running one at a time.

If you pull a plug wire and the engine continues running just like it is now then you've found the cylinder with the problem.

If it runs rougher when you pull the wire then it was working fine.

Careful, don't let it bite you.

How many miles on your injectors?

With you performing a complete tuneup, I would agree that a marginal injector is a possibility here.

The Jeep has 113k on the clock. Why wouldn't it throw a check engine light? And why would it only happen at idle? Could it be that a fuel injector is leaking our partially clogged? Maybe it's time for some 784s

A vacuum leak is most pronounced at idle.

Do a smoke test.