bakulatp

I pulled all my spark plugs and did a compression test.... All cylinders were 160psi. Interesting find though... #5 was getting a misfire code and the spark plug's gap was way to small, almost touching. Thinking I bumped it while putting it in last time I changed them. Made sure all the gaps were good and reinstalled. Cleared codes.

Problem is still there. Now I got a P0305 (still), P0300, and a new one P2172 (high airflow/vacuum leak).

I sprayed around with carb cleaner around my intake manifold, and vacuum lines - found nothing.

My problem goes away after disconnecting the battery also.... ugh...

07 Rescue Green

Well the saga continues, it's back at the dealer, of course no misfire for them while it was hooked up. I have to work the next 9 nights so I can't get down there to get it (hour away), told them to let the mechanic take it home and drive it every day until it happens, he has a scan tool that he can leave plugged in while he's driving it. They think it might be a bad lifter but that doesn't explain it going away (the misfire, not the CEL) when you pull the batt. cables, to replace that the head has to come off again which I will not pay for that to happen. Looking more like the thing is going to get traded in.

hillz

Last winter my 2010 JKU Sahara was misfiring badly and generally running like a__. Took it to the dealer who diagnosed a bad spark plug (relatively new Champion platinums). It was replaced and things seemed to be better. Less than a 100 miles later it was running badly again. Tried cleaning out the engine with Seafoam. Didn't help. My "Torque" diagnostics still showed a misfire on #2. I replaced the EGR and all O2 sensors, suspecting they might be part of the problem. No joy... still ran like cr_p. Started talking to the guys at DUI because I had been running a Firepower ignition for awhile. They were awesome! They sent a replacement set of wires and offered to send a new ignition if that didn't fix the problem. Again, the replacement wires seemed to help... for awhile... #/!@$ Torque showing a problem with #2 still. More talk with DUI... they suggested dumping the Champions for Autolite double platinums. I bought a set of those and installed. At the same time I cleaned the throttle body with Mopar Combustion Chamber Cleaner (Amazon). Problem solved... my beloved JKU runs like new again! Just went over 110k and still getting 20mpg on the highway -18mpg all around. Give the Autolites a try... and the Mopar cleaner!!

07 Rescue Green

Thanks for the response Hillz, glad your issue has been resolved. When this first started last December I had NGK's in it, went to champions then with no change. Since mine is only misfiring on cyl 1 and only right after startup, I tried a bosch plug in #1 with no change. I'm thinking it's electronic since if you pull the battery cables and reinstall it goes away for a couple hundred miles. Dealer can't find any issues, they see the misfire just not what causes it.

hillz

The problems you are experiencing may go deeper, but I also tried NGK plugs during my troubles, before going to the dealer. Just like with some of the other things I tried, the problem seemed to be better temporarily, but then got worse again so I switched back to Champions. I noticed you are running a DUI ignition also. They recommended that I dump the Champions for Autolite because in their experience they just seemed to work better with their product. Might be worth a try.... just sayin'!! Good luck... I hope you get if figured out.

bakulatp

I disconnected my battery for 30 minutes or so...

All symptoms vanished, regained what little low end torque I should have and my mpgs improved drastically...

Already 30 miles over what I normally get on a tank of gas and still have about another 30 to go...

07 Rescue Green

Glad to hear that worked for you, if it works like mine, it'll be back in about 300 miles. I picked up my Jeep yesterday. They said it never misfired once (they had it two weeks and the mechanic was driving it home every day). I'm sure he pulled the battery cable because my central door locks are working again (I posted that in a different thread) so I have a couple hundred miles before it starts up again.

07 Rescue Green

Just an update, still misfiring. I did some testing on my own. I have a spark tester and installed it on cyl. #1, you could definitely see the misfire. Had a thought about what RonJenx said about wasted spark so I used the spark tester and connected #1 wire to #4 coil and #4 wire to #1 coil. Started it up and it still was misfiring but my spark tester showed perfect spark. Hooked up my timing light to #4 wire (still connected to #1 coil) and it was misfiring. So the problem is definitely electrical. I've already replaced the coil and ECM, there are only a couple other things it could be, wiring or TIPM so I ordered a new engine harness and injector harness (just to put all new on the engine). As soon as those get here we'll see what happens. I know that the TIPM in my 06 PT Cruiser needed to be programmed, not sure about this one.

07 Rescue Green

Well the new wiring harness didn't fix it, disconnecting the battery didn't make it go away, it's getting worse, don't know what to do now.

Kojack

first thing, ditch the platinum expensive spark plugs, they are just a money grab for spark plug makers. Get a set of normal copper plugs in there. Copper is the second best conductor of electricity next to gold. You may have to change them more often, but they work better. secondly, check your 02 sensors, mine had a misfire and poor drivability, it turned out that one of my O2 sensors shit the bed.

But number 1, ditch the crap expensive plugs.

EDIT: Just noticed you have the viper TB mod, did you swap back to stock? if not, I am guessing that could be 80% of your problem there too.