Jeep Repair: 02 KJ Cylinder misfire, cylinder misfire, balance shafts

Question
2002 Jeep Liberty 6cyl. auto trans
engine light came on and I pluged in diagnostic to check for error code and got a 0305 code cyl-5 misfire and sometime a 0303 cyl-3 misfire. It is also hard to start when cold. Do you know what I could check to see what would be causing this problem.

Thanks
Bill Heitman

Answer
I would start with new spark plugs.  The Liberty spark plug was originally a Champion plug but they later came out with NGK plugs to be installed in place of the Champions.  A software update for your engine control module might be required as well.  How many miles on the car and what's the tune-up history?

I think this is a long shot but one of the last classes I went to before leaving the dealership life was on the newer engines including the 3.7, 4.7 engines.  Both have balance shafts and they said they could be out of sync.  Don't put alot of money in this idea just yet but I wanted to throw it out there in case I forgot later on.  Most noticeably this was felt as a rough idle and not so much of a mis-fire.
Doug