TJ: Rough idle/misfire

[Nipple Twister]

I was wondering if anybody can help me out here?

I have a 06 Rubicon with 50,000 miles on it which has started to run rough and eventully the Check Engine light came on.

I have a "Actron CP9125 OBD II PocketScan" which displayed the following:

2 codes
P0304
P0304
MIL ON
MONITRS
2 INC
EVAP
02 HTR
5 READY
MISFIRE
FUEL
COMP
CATALYST
02 SNSR


The data base I have said P0304 is "Cylinder 4 Misfire".
So right now I thinking coil pac, injector nozzle, 02 sensor/s (4)


Can anybody else make sense of this? Thanks in advance for any insight.......

[alittleoff]

I had about the same thing happen to mine just before a smog check. #3 spark plug, the main electrode was broken and loose inside the ceramic housing. I replaced all 6 plugs, cleared the codes and passed smog. HTH.

Steve

BTW, all sensors (4) and coil packs checked out ok.

[Nipple Twister]

Hey Steve, you nailed it. Changed all six and now she seems to be humming right along. I have never had a plug fail like that.....thanks for the reply and the info........I installed these E3s about 10,000 miles ago, never noticed any improvement and now this. I'll stick with OEM from now on.........

[Ol Man]

I see on a number of forums that people have issues with E-3 plugs.

[alittleoff]

Cool... My trouble was with the E-3's too. Autolite APP's installed now.

Steve

[Jeeperator]

I and many others have had the same issues with bosch platinum plugs also. Do not use those ever!.

[chris142]

The 4.0's with the coil on plug ignition don't like single Platinum plugs. You must run a regular Copper plug or a double Platinum. Many plugs such as the Bosch Platinums and the Autolite AP985 are a single Platnum plug and those won't work. The double Platinum APP985 will work fine.

I'm bad at explaining stuff but here goes.
The engine has 3 coils and 6 spark plugs. This means that it fires 2 plugs every time it fires a plug. When you get a single Platinum plug or a Multi electrode plug such as the E3 it will misfire. The misfire is caused by having different metals and the coil trying to fire both plugs. One plug fires + to - and the other fires - to + at the same time!

The different metals cause a resistance change and this goofs up the spark for lack of better words.

[6spdYJ]

Many of the ignition systems use mulitple coils to extend the dwell to an individual plug. It's a smog thing. They fire a plug twice, once to start combustion, and once to assist burning remaining gasses, it's not necessarilly timed to provide a hotter initial spark. All they do is fire a non-active coil (providing initial spark) to a spark plug which is nearing the end of the power stroke. It's essentially a dead fire, but doubles the duty cycle of a plug - which causes heat through the electrode thus wears them out faster if they aren't up to the task.

I had a set of Bosch platinums actually burn the electrode inside the insulator and drop them into the cylinder. No spark. And that was on a small-block Chevy with HEI, no MSD or anything fancy. I learned to stay away from the super-duper gizmos and just play with heat ranges on stock designs.

[Jeeperator]

I had a set of Bosch platinums actually burn the electrode inside the insulator and drop them into the cylinder. No spark. And that was on a small-block Chevy with HEI, no MSD or anything fancy. I learned to stay away from the super-duper gizmos and just play with heat ranges on stock designs.

Thats sounds exactly what happen to me but I thought the skinny platinum electrode wore out inside the insulator because if I close the gap real tight they started working again. Its happen to me twice with those plugs but never again. A buddy who owns a local smog shop says there O2 sensors are crap too.

[6spdYJ]

Unless the OEM calls for platinum, (Ford uses double platinum) just stay with what worked before. If I'm not mistaken, copper has the best conductive properties through all heat ranges. Obviously aluminum conducts better - but it can't hold up to heat. That being said, I see the fancier stuff as just a faster way to throw away money. We do it at the pump enough, no need for a two-front battle.