I have an '04 Wrangler Sport with the 4.0L and am having trouble with cylinder 4 misfiring. I have taken it to 3 different dealorships and they can't seem to figure out what is wrong with it. When I start it cold in the morning it runs good. Once it heats up however it starts missing and the check engine light starts flashing. When this happens my RPM's will not go over about 2900, it feels like a rev limiter is kicking on or something. So far two of the dealorships have said that the plugs could be bad but they were brand new (2 weeks old), and one has said that it was the coil pack. I have since spent the $150 on the coil pack to no avail. Last year the hydrolic lifter and cam shaft for the same cylinder were replaced. If anyone has any idea on what I may be able to do I would very grateful.

Thanks  

it could be somthin simple like a cracked porcelin on the s/plug...even though they are new it couldve been touched just right w/the socket to do such a thing...  

run some injector cleaner thru your gas tank.
what you have is a clogged injector on #4  

i second the injector notion.  

I have been running cleaner through it at regular intervals (about once a month), it seems to help for a day or two and then goes right back to the problem. If the injectors are the problem and that is not fixing it the next step would be to replace the injectors correct?  

i would assume if you took it anywhere good they would have checked your coil pack (you have the one that runs across all your plugs with all the boots right on it), spark plugs, and injectors. Did they replace anything going by your last post they at least didnt change the injector, but you i would have hope at least changed the spark plugs for $20, and a coil pack runs ya between $140-$180 and must be changed as regular maintenance so its not a bad investment. if all of this is done and its still a problem my buddy had the same problem so i wouldnt doubt it i would say its an electrical problem and best left to the dealer    

ive seen the same symtoms with a cracked plug or bad plug wire.loosn the plug wire where it is just on the plug and easy to take off.then start it and pull it off with a pair of pliers.if you got shocked its likeley the wire.if it doesnt make a diff.it could be the plug.ck. the compression on that cyl.  

Brendan,  I have replaced the spark plugs and the coil pack and yeah it is the single bar going across with all of the boots. The only thing left on your list of replacements is the injectors.