#5 cylinder misfire & secondary coil ground fault

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M&M's13JKUS

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Howdy!

I'm an old school diesel guy, so I'm a bit out of my depth.

Just bought our first wrangler. 2013 jku Sahara manual 38,00 mi. Love it except for this issue which has me bewildered.

I've replaced the spark plugs with ngk ones. Swapped the coils from 1 to 5 and the problem remained. @ no. 5. That's when I notice somebody did a hack-job trying to splice a "new" coil plug-end into the wiring harness. Im pretty sure the bare wires made contact. (I'm guessing the original plug end may have gotten damaged so it was necessary to replace trying not to do the whole harness) I have since attempted a nicer repair with butt splice crimp connectors, ALSO it sounds like bad rocker arms with the pentastar "tapping" sound.

The check engine light will come on right away or as many as 40 miles after being cleared. It seems to trigger more quickly when running the air conditioner? I haven't gotten a FSM yet, but I have some theories on what may be the cause:

*ECM - why problem so spuratic.
*Vacuum leak.
*Bad injector #5
*Valve issue in #5 because of the rockers or other compression problem.

With the factory wiring having been compromised for reasons I am un-aware, I wonder if the wiring harness may need to be replaced?

PLEASE any of you tinkerers out there! Anything to try or test I'll do if i am capable.
 
M&M's13JKUS said:
Howdy!

I'm an old school diesel guy, so I'm a bit out of my depth.

Just bought our first wrangler. 2013 jku Sahara manual 38,00 mi. Love it except for this issue which has me bewildered.

I've replaced the spark plugs with ngk ones. Swapped the coils from 1 to 5 and the problem remained. @ no. 5. That's when I notice somebody did a hack-job trying to splice a "new" coil plug-end into the wiring harness. Im pretty sure the bare wires made contact. (I'm guessing the original plug end may have gotten damaged so it was necessary to replace trying not to do the whole harness) I have since attempted a nicer repair with butt splice crimp connectors, ALSO it sounds like bad rocker arms with the pentastar "tapping" sound.

The check engine light will come on right away or as many as 40 miles after being cleared. It seems to trigger more quickly when running the air conditioner? I haven't gotten a FSM yet, but I have some theories on what may be the cause:

*ECM - why problem so spuratic.
*Vacuum leak.
*Bad injector #5
*Valve issue in #5 because of the rockers or other compression problem.

With the factory wiring having been compromised for reasons I am un-aware, I wonder if the wiring harness may need to be replaced?

PLEASE any of you tinkerers out there! Anything to try or test I'll do if i am capable.
Click to expand...


Your in my boat old school diesel guy, Cummins here.

Since you know the problem stays at no 5 cylinder I would check the wiring real good for that cylinder. Make sure there isn't any bare going to ground. Also make sure the connectors they used have the wires crimped tight and be sure the are the heat shrink type.
 
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BLACKJKU said:
Your in my boat old school diesel guy, Cummins here.

Since you know the problem stays at no 5 cylinder I would check the wiring real good for that cylinder. Make sure there isn't any bare going to ground. Also make sure the connectors they used have the wires crimped tight and be sure the are the heat shrink type.
Click to expand...
Yessir! 4bt or 12 valve would solve this problem! 😆😆

That's a good idea, maybe there is another problem with the wiring up stream from the plug. I will check. Thank you 🤞
 
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M&M's13JKUS said:
Yessir! 4bt or 12 valve would solve this problem! 😆😆

That's a good idea, maybe there is another problem with the wiring up stream from the plug. I will check. Thank you 🤞
Click to expand...

When my JK gives me to much problem with electrical or the engine it'll be a 4bt, been looking for one for some time now to have one ready. I have a 12v that I could put in it but it's to long and no room for a big enough radiator.
 
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Took the jku on a road trip yesterday. It could have went better.
So far I haven't seen or found any more suspect wiring issues pertaining to the p0305 code.

I have an INNOVA 3040e+ scan tool. When I erase the codes either :
"P2314 ignition coil secondary circuit "
stays on OR
"P0305 misfire detected"
stays on, but the Check Engine Light (CEL) sometimes turns off.

I have resorted to disconnecting the battery and resetting the ECM which SOMETIMES seems to make the engine run 90-95% ok (engine still doesn't quite feel correct though) for about.... 10-75 miles. I am really hoping and thinking it's the ECM since it runs so we'll usually after being reset. It feels extremely hot to the touch.

Looks like I can get a Mopar ECM for about $500 😬...

Does anybody have a recommendation for a way I, or company could run a diagnostic or somehow flash it to see if things improve?
ONE LAST THING my reader gives values on the live data as follows:

O2S B1S1 .075-.800 VOLTS
STFT B1S1 -0 TO -4.7 %

O2S BIS2 .800V **(UNCHANGING)
STFT B1S1 99.2% **(UNCHNG)

I ADDED THE ** UNCHANGING
what could that mean?
 
Did you ever figure it out I’m having the same problem with a 13 jku. P2314 and p0305b. Also has po420 and po430 for cats. I have replaced coil packs spark plugs and catalytic converters. My pcm is also runs hot. I changed my asd relay and it runs better temporarily
 
Chris81579 said:
Did you ever figure it out I’m having the same problem with a 13 jku. P2314 and p0305b. Also has po420 and po430 for cats. I have replaced coil packs spark plugs and catalytic converters. My pcm is also runs hot. I changed my asd relay and it runs better temporarily
Click to expand...

Did you put factory cats on or Aftermarket ones? I have high flow Cats on my JK and had to put o2 foolers on the 2 down stream o2's.
 
Stock replacement cats. They are off eBay but bought from a Canadian seller not China and it’s throwing exact same codes with all the changes. I’m more worried about the misfire now. The computer thinks it has one so it’s shutting #5 down.
 
I haven't swapped coil packs....the new one I replaced on 5 with didn't solve the problem...I may swap them out to see if it isolates cylinder and eliminates the coil....I was wondering the spark plug gap was off but this issue is so sporadic when it's actually misfiring. I'm wondering about fuel or the vacuum line which I've read about. Not feeling the "jeep" experience.
 
Mine was running great changed all coil packs and plugs. Was running great then the computer shut down cylinder 5 I work 30 miles from work so wife picked me up with truck and car trailer. It’s probably in your wiring take that flat plug on intake manifold apart and check pins for corrosion
 
Chris81579 said:
Mine was running great changed all coil packs and plugs. Was running great then the computer shut down cylinder 5 I work 30 miles from work so wife picked me up with truck and car trailer. It’s probably in your wiring take that flat plug on intake manifold apart and check pins for corrosion
Click to expand...
Did u just clean it with a brush and what cleaner did u use?
 
This plug?

20230822_190912.jpg
 
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