How many miles are on it? There is no single ignition coil like older cars had, it has three ignition coils that are shared by the six spark plugs which is called a coil pack. The coil pack isn't normally considered a tune-up item, I'd first just replace the spark plugs if they have many miles on them and see what happens.
One thing to keep in mind is that 2000 and newer TJ 4.0L engines are very fussy about which spark plugs they like to run well on. While this isn't a complete list of suitable spark plugs, the following three are well proven to work and perform very well for at least 100K miles... Autolite XP985, Autolite APP985, or Champion 7034. Caution not to use single-tipped platinum plugs like the Autolite AP985 or Champion 3034. Avoid Bosch plugs too, especially Bosch's Plus-2 and Plus-4 plugs.