Hello I have Jeep Wrangler 2006 and I have seen seen an error P304 What is the problem. Thanks

The p0304 code is a misfire on cylinder 4 (the last number indicates the cylinder). Check the plug and compare to the others. The plug should be a grey peach colour. Now check the plug lead end socket. There should be no signs of tracking through the insulation to the cylinder head. Check the high tension lead resistances. If lead 4 is much higher resistance than the rest, replace it. Now take a look at the distributor cap, make sure that there are no signs of tracking on the interior or the cap is cracked. Ensure that the contacts and distributor arm are clean and free of build-up. Since the error is specific to one cylinder it is likely that the coil is OK.