Jeep Wrangler Forum banner
  • Hey everyone! Enter your ride HERE to be a part of JUNE's Ride of the Month Challenge!

1 - 8 of 8 Posts

·
Registered
Joined
·
80 Posts
Discussion Starter · #1 ·
Hey Everybody, I'm usually over in the TJ forums, but today it's my wife's JK that's acting up. Last week she started getting a PO303 #3 Misfire and it was driving rough, okay, no biggie right, change the plugs and coil packs while I'm there. They were overdue anyway. Got 6 Champion RER8ZWYCB4 and 6 new Bosch coil packs. 4 hours later all buttoned up with no real issues, although it's ridiculous what you have to do to change the plugs.
Runs fine for a bit, quick roadtest. Then the next day we go out to run some errands and get a PO302 code and it starts running rough again. Today I pull it all apart again (much faster!), check the plug gap and replace the coil pack with another one I got from Advance. Looks just like the Bosch, made in Brazil, etc. The plug was spotless, almost like it hadn't fired at all. Buttoned it back up and fired it up. Same thing, PO302 code and it runs rough.
Any suggestions? Could the plug be bad? I don't have anything to go chasing down a bad wire connection or something, so if it's electrical I'm pretty well screwed. The connection on the coil pack seemed solid and clicked home. Thanks!
 

·
Retired Moderator
Joined
·
100,473 Posts
Rather than throwing parts at it, just take it into your dealer and have them diagnose the problem. Then you will know what you are dealing with. This maybe cheaper in the long run.
 

·
Registered
2015 JKU Willys Wrangler
Joined
·
241 Posts

·
Registered
4 Jeep family
Joined
·
282 Posts
Had that code pop up when I bought my 2012 JKU. Long story short, mine needed the cylinder head replaced. Good news (depending on your mileage), is they extended the warranty to 10 year or something like 125k miles. There's a service bulletin that explains how the dealer determines if its the head (I think it was with a leakdown test). Good luck.
 
  • Like
Reactions: Muffin Top
1 - 8 of 8 Posts
Top