There is a long black item on the passenger side of the engine. That is the coil. They are under it.
A Jeep Wrangler has one spark plug per cylinder.
Six
spark plug loacation on 2006 jeep wrangler sport 4.0 liter engine
A swivel spark plug socket will let you get to #1.
.035 in GAP
Hopefully this will helphttp://www.4x4xplor.com/sparkplug.html
Great link that someone posted on everything you need to know on changing your spark plugs! http://jeep.us41.org/sparkplugs/index.html
Use the same spark plug that came in it, Champion for best results.
.035 is the correct gap for your Wrangler's spark plugs. That gap is correct for at least up to 2006 and likely for 2007-2009 as well.
The 2003 Jeep Wrangler has 16 valves.
For both 4 & 6 cylinders, they are on the passenger side of the motor. Follow the plug wires to the plugs in the side of the engine.
The 2003 Jeep Wrangler is a gas-powered vehicle.