I need help.....When my car warms up (TJ 3.5) and I leave it to idle, it starts to fluctuate between 500rpm and 1200rpm up and down. It doesn't always do it.
Has anybody ever had this???

Are all your 'tune-up' items and sevices up to date ?

Had a tune up 2 months ago

Do they do anything to the computer or plug something to the car during a tune up?

Sounds to me like the ISC (IDLE SPEED CONTROL) has shat itself.

Is that part of the throttlebody? Where can I find it? How much does it cost to fix/replace?