jeepers10

I used NGK plugs it called for and gapped at .040 i am just at a total loss

King04WJ

The problem with the WJ, as with any Chrysler vehicle is that they are finicky about the parts you interchange. Just like with the O2 sensors I recommend never strating from NGK as this will most definitely draw up codes. The Jeep does not like the Autolite or especially Champion, this will cause other codes to surprise you for no reason. I hope this information does anyone some justice.

Cherryokee

All this stuff about plugs and coils may be valid but still, how did you get here? Did your mechanic use a CPS from the OEM (original equipment manufacturer)?

Aftermarket CPS often fail to meet spec, causing other problems which mislead diagnostics (thus causing us DIYers to fire the parts cannon repeatedly) and they break down early.
If you can determine that the mechanic used an aftermarket CPS (i.e., not Mopar) then you may have solved the problem (after you replace it with the OEM part from Mopar).

Marwell_Grimes

I know this is an old thread but not a dead topic or problem.
I agree with any sensor you should use Mopar OEM or equivalent Delphi/Motorcraft/Denso. Never use aftermarket brand sensors in your WJ!

There are 4 main paths that cause misfire. Ignition, Fuel, Cylinder Compression, and Exhaust stroke.
One of these is always the problem and you must do tests for all possible paths to find and confirm what it is.
If it was a ignition coil, swapping the pack would confirm it without having to use a Oscilloscope.
If it's a spark plug you can swap with a cylinder that doesn't have a misfire and if the misfire jumps code to the cylinder you borrowed the plug from and disappears from the bad cylinder. Then you can be sure the problem is that spark plug. No $ or purchase required.
If you need to see DTC's for free simply switch key to on then off rapidly 3 times ending with key on and you will see your codes in the place you normally read Odometer.
Then do a cylinder compression test with a $17 tool.
Test fuel injectors, you can do this with multimeters but the most accurate way is a O-Scope that reads under a millisecond. They cost $100 for an entry level 2 channel Oscilloscope. You can compare each injector to the other, then compare it to the known good plug signal and you should get near identical readings except for the ignition coils primary coil collapse charging the secondary coil shown in an oscillating pattern on graph.
If one is not like the other, clearly something's wrong with that Injector/Ignition coil/Spark Plug.
You can also do a simple spark plug test.