Bank 2 misfire

[Ski6]

2006 history: over a year ago, I replaced the head gasket along with all the usual components while I was in there. Heads were resurfaced and checked out. Ran great for over a year.
Now I have a reoccurring misfire that starts with #2. Idles rough, but runs great otherwise. When reading live data, I can see the misfire counts on on Bank 2. Mostly #2 followed by #6, then #4.
Tests I've performed. Compression, leak-down, vacuum leaks, cleaned injectors and swapped banks, swapped coils from one side to the other, correct NGK plugs are in (gaped at 40), exhaust back pressure (there is no lack of power). I can't visually see anything wrong with the wires, but what's the chances/commonality of the entire Bank 2 wires being bad. Everything checks out good. Fuel trims numbers are the same on both Banks.
I am at a lost and looking for ideas. Computer?

 

[LibertyTC]

Welcome to the forums.
Just because you can view random misfires, does not necessarily mean there is a serious problem.
It can take 1500-2000 sensed misfires, to set an engine light. Does the engine light come on /set a misfire code?
Rough idle: Is it a lite engine shake at idle? Or rpm falls = almost stalling ?
The IAC (intake air control) controls the idle and cleaning the throttle body, IAC port, (can often get gummed up with carbon) can help.
Also consider replacing all 6 coil packs, consider this a tune up item, as they fire the plugs hot and new coils may smoothen out the idle.
I got away using new Standard brand coil packs, even tho Mopar packs are the best.
Also check the PCV valve, is it clean/rattle?
Try not to let the jeeps idle too long, they like to be driven, & blow the dust out at higher rpm's.

 

[Ski6]

Yes, the engine light is on. Will come on after about 20 miles indicating cylinder #2. after a more miles #6 will trigger the random misfire.
When I did all the work on it last year, the PVC was replaced and throttle body and IAC were cleaned. The entire top of the engine is spotless.
I hear what your saying about the coils as a tune-up, but for troubleshooting purposes, without throwing money at it, I'm quite certain that's not the issue since I can swap them without the problem following them.

 

[sleazy rider]

What spark plugs are in it and have you physically looked at the electrodes?

The recommended plug is NGK ZFR6F-11G.


(plug number fixed)

 

[LibertyTC]

Yes with codes set that is not good news .
Yes remove spark plugs for inspection I'd like to see pics of condition.
Did you rebuild the heads ?
Or is there any warranty applicable?

 

[Ski6]

I can grab a pic later today.
Heads were sent to a shop where it was surfaced, pressure tested, and valve stem seals replaced. I guess that's considered rebuilt?

 

[LibertyTC]

Sure let see all 6 plug's condition pic, note each cyl location if possible. Measure gaps too.

What spark plugs are in it and have you physically looked at the electrodes?
The recommended plug is NGK ZFR6K-11G.

Close but the correct spark plugs for the KJ from under hood sticker is:

You must be registered for see images attach

 

[sleazy rider]

/Get Smart voiceover

Missed it by that much.

Oops.

 

[Ski6]

Didn't fix or forget about this. Weather hasn't been cooperating lately. Will get pics of plugs and do a sanity check of compression soon.

 

[Ski6]

Update. Spark plugs were all good. All looked exactly the same. I’d add a pic, but can’t seem to get it small enough via my phone. But really, nothing to look at. They are the correct plugs.
I did perform another compression test and I do have an issue on #2. It’s reading 110 while the others are between 150-155. Will perform a leak down test next. May be rebuilding in the spring.

 

[LibertyTC]

Ya only a variance of 10 % is acceptable, somethings definitely up with cyl #2.
Have a peak under the valve covers, check rockers, nothing loose or off?

 

[Ski6]

Everything looks good under the cover. When I first bought it it had a blown head gasket and a thrown rocker. So I knew to look for that rocker. And all sounds fine under there, no rattling.

 

[ltd02]

Might have tweaked a valve seat so it won't close completely. Don't want it to drop completely or you'll really screw things up. This was a common issue on the very early KJs but maybe the bad HG and getting it hot added to the issue in your later 06.

 

[Ski6]

I had all the seats taken care of when I did the head gasket. Unfortunately I’m pretty certain it’s the ring. Injected air at its TDC and i only heard it coming from the dipstick tube and oil cap.

 

[LibertyTC]

How many miles on your KJ? Unfortunately @ 110psi the #2 rings could be toast.

 

[hecate]

I had all the seats taken care of when I did the head gasket. Unfortunately I’m pretty certain it’s the ring. Injected air at its TDC and i only heard it coming from the dipstick tube and oil cap.

hey, did you figure out if your misfire issue was due to the rings on #2 cyl? i have the same issue with 2,4,6 but dont see how bad rings on cyl 2 would impact misfires on 4 and 6 as well.

 

[Ski6]

hey, did you figure out if your misfire issue was due to the rings on #2 cyl? i have the same issue with 2,4,6 but dont see how bad rings on cyl 2 would impact misfires on 4 and 6 as well.

Funny you should ask. Just finished my casual (worked on it when I had time) rebuild. Running well with no lights, then…light comes on for misfire. Son of a bi@$&!! Cyl 2 & 6 still. Barely 4. I’ll be doing some troubleshooting today. Did order a new cam sensor since it’s been so long and it’s not in my log as being replaced yet. But I figured that would affect more than the one side. Wish I had that head tested again while it was off the car. I’m leaning to a bad head even though a shop did a complete head job on it. Stay tuned.