Cylinder 6 Misfire

[BrandonM]

Now, before any of you say "search" I did search. Ive been chasing this damn cylinder 6 misfire issue for months. I have swapped out all of the spark plugs, replaced #6 coil pack with a brand new one, and just yesterday I replaced all of the injectors.

No CEL for 2 days, then last night the wife was driving it and it threw a code again. Low and behold.... same code as before.

So, Im at a loss now. What more is there to do? Wiring to the injector? Wiring to the pack?

Thanks...

 

[BrandonM]

19 views, and no ideas? LoL, thats kinda where im at too...

 

[Dave]

Yeah, you changed everything I can think of.

Dave

 

[BrandonM]

There was one other thing I thought about changing, and thats only because I remember coming across a thread somewhere about it, but one of the o2 sensors. Does that sound like a viable option?

Other than that slight possibility, I guess I could be looking at a valve job?

Oh, and as for the wiring option (which I plan on looking into tomorrow) does anyone have any troubleshooting tips for the injector and coil pack wiring?

 

[seabass1858]

Could it be in your PCM?

 

[SabaII]

I am actually going through the same as you only on cyl #4. It will misfire on start up then either go away right away. Or it will keep missing until I turn the car off and then back on and it goes away. I could use some insight. I thought about possibly if the battery is going weak or alt that could be messing with my voltages enough to cause the computer to act up.

 

[BrandonM]

I have trouble believing its a pcm issue only because its so intermittent. It literally runs fine. Only occasionally will it stutter and buck and require me to pull over, shut her down, then restart. Open startup, its always back to being good to go again.

I would think if it were a pcm issue, it would be more constant.

 

[sswk06]

Had the same intermittent issues a while back. One day the code stayed on but the Jeep ran fine. Replaced everything like you did - ended up with a valve job - possible valve spring issue. The intermittent sputtering from the tailpipe was a clue. After new heads the Jeep is smooth as silk - no tailpipe sputtering. Good luck!

 

[BrandonM]

Had the same intermittent issues a while back. One day the code stayed on but the Jeep ran fine. Replaced everything like you did - ended up with a valve job - possible valve spring issue. The intermittent sputtering from the tailpipe was a clue. After new heads the Jeep is smooth as silk - no tailpipe sputtering. Good luck!

So you got a valve job AND ended up having to buy new heads? Or, was the valve job good enough?

 

[rockymountain]

Any coolant loss? I think someone before had a bad gasket and it was leaking coolant into the cylinder which would eventually make it misfire. Throwing that out there since you said it was fine for 2 days before it came back.

 

[BrandonM]

Nope. No coolant loss at all.

 

[SabaII]

What I am stuck on is if it were a head issue you would think that shutting it down then re-starting would have no effect on it. I have been known to be wrong before but it sounds more electrical to me.

 

[BrandonM]

What I am stuck on is if it were a head issue you would think that shutting it down then re-starting would have no effect on it. I have been known to be wrong before but it sounds more electrical to me.

I agree with the electrical hypothesis for sure, just not quite sure it sounds as extreme as pcm. I also agree with the head issue. If the valve or head were bad, why does a restart clear it? And not just clear it, but it doesnt have another issue for damn near months. I would think if the valve is bad (or valve spring or what not) wouldnt it be bad all the time?

So, my question is still, if I were to trouble shoot the coil wiring or the injector wiring, what voltages am I looking for? Or, should I ohm them out? If ohm, then, again, what tolerances should I be looking for?

 

[sota]

throwing this one out there.... where's the ground wire for that head located?

also I'd check the electrical connector for that coil and injector.

 

[BrandonM]

Well, so far so good. Ive noticed if we let the jeep warm up a bit, and then run it, we dont have issues.

 

[BrandonM]

...... so much for that..... friggin got a CEL yesterday.... No bucking though. CEL just came on, so I wonder if its still gonna give me a cylinder 6 misfire code. My last ditch thought is the o2 sensor, as I believe I read on here that it could be a possibility.

Anyone have any insight on the o2 possibility?

 

[rockymountain]

Cel should indicate a bad O2 sensor if it's bad. Need the code.

 

[Snail Farmer]

It could be your O2 sensors. Check the codes before you proceed. But if you do decide to replace the O2 sensors, do not use anything other than NTK. I found that out the hard way.

 

[BrandonM]

So.... amazingly enough, the check engine light is now off, all by itself. This has GOT to be wiring.... right? One day good, the next day not good? Its got to be indicative of some kind of dirty or bad connection right? I actually have time this weekend to tinker with it so I'll be doing a thorough check of all of the wiring going to cylinder 6 (injector/coil). LoL, it would have to be the most difficult area to get to wouldnt it?

 

[dscott90000]

Where is cyl 6? Pics? I have an 02 . Sure it's the same