P0306 Misfire Help

Artisanau

Member
Joined
Sep 15, 2020
Messages
37
Location
Australia
Hi Forum Members.

Just got home from a trip to the stealership with my 2013 JK throwing out the P0306 code randomly. Can go for weeks or days before replicating with the EML light coming on?

Out of further frustration of the dealer telling me what I already knew for $150, I decided to continue the hunt online with a hot coffee. First post I came to was one from M Duncan 'Matt'.

A thorough explanation and almost similar to mine. Firstly I wondered if he'd resolved his issue as I can't seem to send a reply to his thread? It's probably me, I'm not used to going on these kinds of forums to engage so it's all new, apologies to those who are tech savvy😂 Anyway back on track, I got fed up trying to trace a likely wiring fault with no clue as to what wires were going where with a multimeter, although I did separate clean and check I think, all of the multi connectors. The engine has only done 75'000Km which is nothing. I replaced the plugs due to 4 having a higher resistance than the specs suggest despite the low Kms and changed out the coil but no change as with Matt's JK. I take it to the dealer and end up with them tellIng me what I told them. I think they just put it onto the code reader and didn't look beyond that. I tried talking to the desk supervisor but they don't seem to have the old fashioned people skills they one did. They get easily offended if you try to discuss logic and your car with them.

I assumed when I took it in, it would be put on a tuner where they'd actually look at an oscilloscope etc to determine wether or not it was actually misfiring which it doesn't seem to be, it purrs as it's always done. They want $500 to do a bypass test and compression but I think if I had an issue with the mechanical side you'd know about it, ie, the left cyl head issues re' Mexico builds etc and the fact it's intermittent too makes me think wiring or maybe PCM?

The PCM On occasion seems to get very hot behind the screenwash bottle with the heat coming up from the exh manifold and I'm wondering if maybe that's effecting the coil switches or switch for cyl 6 inside especially at idle in traffic with limited air flow through the engine etc. Any help or suggestions likewise I'll investigate. Apologies for the long winded explanation, next time I'll try and abbreviate as best possible. Like Matt, I feel the same about owning my JK, I won't part with it and want to persist in finding the fault but without the help of the dealership. I'm going in! 👊

Thanks Mark.
 
If I’m not mistake , P0306 means specifically a misfire in 6.
Main causes from easy to find to harder Plugs-Plug Wires-Coil Pack.

Then I’d look at a fuel injector on 6 (It runs well, there are ways to clean, maybe it’s that)
This is a generic “chase down vacuum leaks article I’ve used.
then a vacuum (which actually Is a place I’d look).

Last is crank shaft position sensors. They can go and read wrong and start causing issues.
Unfortunately this isn’t a here’s the symptom, here’s the issue.

You’re gonna have to “go on a walkabout” in the Jeep to find it - see how I my the Croc Dundee reference there? Ha

Good luck and let us know, I know the frustrations, wish I was able to pinpoint More.
 
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😂 thanks for your input 'cpwolf'. Yeah it's bit of a mine field. I thought if it was the crank sensors a code would of been picked up by the dealer earlier today but I can't rely on them. I'll get stuck in over the weekend and see if I've over looked something and I'll double check for vac leaks but like I say it runs as smooth as silk so it's a mystery but I'll re post if I cure it. 👍
 
If you do replace parts don't go cheap because they probably will still throw codes. Buy OEM and you won't have problems.
 
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No
😂 thanks for your input 'cpwolf'. Yeah it's bit of a mine field. I thought if it was the crank sensors a code would of been picked up by the dealer earlier today but I can't rely on them. I'll get stuck in over the weekend and see if I've over looked something and I'll double check for vac leaks but like I say it runs as smooth as silk so it's a mystery but I'll re post if I cure it. 👍
i just got the p0306 code on my 2017 . Did you take care of your issue? Can you share what you have done to fix this issue? I have read up on this but seems like most people changed out their spark plugs, coils, injectors and still had the problem. Any recommendations? TIA
 
I can't remember where but I read about a similar problem and it was solved by rapping heat resistant tape around the wire loom and connectors on the right side of the engine. Might be worth a try.
 
No

i just got the p0306 code on my 2017 . Did you take care of your issue? Can you share what you have done to fix this issue? I have read up on this but seems like most people changed out their spark plugs, coils, injectors and still had the problem. Any recommendations? TIA
Sure did.. new cylinder head done the trick. Good luck 🤞
 
Sure did.. new cylinder head done the trick. Good luck 🤞
I think that’s the problem with mine. I’ve replaced the coil, plugs and checked the injector on cylinder 6 but still have the same problem.
Were you able to get that left cylinder head replaced under Jeep’s special warranty? I’ve heard that Jeep issued an extended warranty just for the left cylinder head. Anyone go with this process?
 
I think that’s the problem with mine. I’ve replaced the coil, plugs and checked the injector on cylinder 6 but still have the same problem.
Were you able to get that left cylinder head replaced under Jeep’s special warranty? I’ve heard that Jeep issued an extended warranty just for the left cylinder head. Anyone go with this process?
Also have a jeep wrangler 2017 with < 50k miles experiencing the same problem. Vehicle is at the dealer and they are getting ready to take it apart. Anyone aware of this “special warranty”
 
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If the dealer is taking it apart Leslie, I’m assuming they’ve called you to suggest what they suspect is the problem and discussed either the related cost to repair or option of warranty if they feel it’s a build defect, no?
 
Received message that they are investigating issue with cylinder 6 misfire and would need to remove the cylinder head to investigate further. No mention of warranty or costs yet. As this appears to be an ongoing issue with this engine I think they should be open about cause instead of saying they are “investigating”.
 
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There’s a procedure they follow which as far as I’m aware 1) to verify the fault code, 2) carry out a comparative leak down test between all 6 cylinders. If the valves and or seats on 6 are burnt/damaged beyond serviceable, it will be evident showing the % of loss on that cylinder and any others with similar results or heading that way. All this is done prior to the cylinder head tear down.
Looking at your situation in a positive light, I’d want to assume that they know the results as negative and are just pressing on with the job knowing it will be covered by Chrysler warranty. Good luck and keep us posted on the forum won’t you 👊
 
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Leslie, in Connecticut, how you doin with a response from the dealer on your Jeep.
Received message that they are investigating issue with cylinder 6 misfire and would need to remove the cylinder head to investigate further. No mention of warranty or costs yet. As this appears to be an ongoing issue with this engine I think they should be open about cause instead of saying they are “investigating”.
I’m hoping your back on the road by now. Maybe you could give me an update of any progress. It’s frustrating beyond belief and that’s if you can do a fair bit of diagnostics yourself, let alone if you’re solely in the hands of a dealer or specialist outfit. Finger crossed here in Aus 🤞
 
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Also have a jeep wrangler 2017 with < 50k miles experiencing the same problem. Vehicle is at the dealer and they are getting ready to take it apart. Anyone aware of this “special warranty”
Our 2017 with 60,750 miles threw the P0306, shop did the plugs and coil packs, that wasn't it. Suggested speaking with FCA to work out a discount based on the 750 miles over warranty. Was basically told to go pound sand, Replaced cylinder heads and oil cooler since it was broken apart. I unfortunately love this jeep. But posting here to see how many others are having the same issue with this year and engine.
 
So it’s 100% fixed your symptoms as a result baristabob? What about the question of warranty then. Did FCA come to the table and take care of you. These answers are as important as the fault issues, ‘cos Jeep owners are also reliant on the confidence that FCA will standby them as expected they will, without having a breakdown in the meantime, considering they generally made a hefty purchase on the basis that they will. 👊
 
So it’s 100% fixed your symptoms as a result baristabob? What about the question of warranty then. Did FCA come to the table and take care of you. These answers are as important as the fault issues, ‘cos Jeep owners are also reliant on the confidence that FCA will standby them as expected they will, without having a breakdown in the meantime, considering they generally made a hefty purchase on the basis that they will. 👊
FCA will get nothing but bad press from me the rotten scoundrels. Filed a customer service inquiry, nothing. And that was what the no good Bill Luke Service manager suggested after saying oh well, nothing we can do.
2 weeks in the shop, my local shop replaced the heads, no sense having to back in for the other and upgraded the oil cooler too.
Warning, have your compression tested before the warranty lapses.
 
Unreal. No manufacturer is without recalls and warranty issues, but it’s how they deal with them and take care of their customer base that must be relevant to future sales and success you’d assume. Maybe not in the case of Jeep. Maybe that’s why I read their sales figures are nose diving?
At least it’s on the road again and with the contact base via these Jeep forums, you might tackle some mechanical issues and diagnostics yourself and find a good reliable enthusiast independent for the more difficult tasks. Hang in there 👊🍻 Life’s Good
 
Our 2017 with 60,750 miles threw the P0306, shop did the plugs and coil packs, that wasn't it. Suggested speaking with FCA to work out a discount based on the 750 miles over warranty. Was basically told to go pound sand, Replaced cylinder heads and oil cooler since it was broken apart. I unfortunately love this jeep. But posting here to see how many others are having the same issue with this year and engine.
Pentastar V6? Friend had same problem and was just past warranty. Filed claim with Mopar who chipped in > $3,000 for $5,500 repair.
 
Pentastar V6? Friend had same problem and was just past warranty. Filed claim with Mopar who chipped in > $3,000 for $5,500 repair.
Leslie, do you know who, what, where on that process and was it for one after 2013 model? I ask because I think I filed a claim, but FCA Customer support was very sketchy and the email they gave to upload the diagnostic had to be modified 8 times before I did not receive an error. So I don't know if it made it to them. If there is another method I'd love to recoup something.