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Old 05-18-2013, 10:42 PM   #1
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p0303 code

I bought my 03 wrangler over a year ago with 137K on it. I now have 140K on it and this week I had my first issue. Drove it around town and stopped at the store. Fired it up and it stumbled badly. Threw a code P0303. I know this is a misfire on cylinder 3. I assume cylinder 3 is third from the front. I pulled the coil pack rail and noticed that the boot on the third from the from was discolored (maybe from heat?). I swapped 3 and 4 spark plugs(They looked fine) and it seems to idle fine. Haven't driven it yet to get it hot. I do not know when the plugs were changed. What recomendations do you have. Start with plugs or change both the plugs and the rail? Also how do I reset the code?

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Old 05-19-2013, 04:56 PM   #2
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Had this code on 2004 TJ. Check out Jeep service bulletin 18-031-03. Rough idle after hot soak. Install fuel injector insulator sleeve part # 56028371AA. Try to stay away from fuel with 10% ethanol (I use BP, my TJ seems to like it best)

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Old 05-19-2013, 08:45 PM   #3
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I expected more replies but thanks GDAWG. I swapped 3 and 4 cylinder plugs and no issues. Mayne trash in the injector? I just seafoamed the tank. I will checkout the tsb for sure.
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Old 05-19-2013, 09:17 PM   #4
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If swapping the two plugs fixed it you may have a carbon track on the plug and inside of the plug boot, now that you've swapped them the two tracks no longer line up and cause the coil to short to ground.
If you noticed a line down the plugs ceramic you need to replace both the boot and plug or it will return..
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Old 05-29-2013, 12:23 PM   #5
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Thanks. I will pull again and check.
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Old 02-28-2015, 07:19 AM   #6
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Have a 2002 Jeep Wrangler. Rough Idle, flashing check engine light, P0303 code.
Replaced Ign Coil Pack which solved the problem.

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