Cylinder 2 Misfire / P0302 on a 2007 JK

So today I was out mall crawling with my 3 month old and on my way home and noticed a drop in RPM's and a severe shake in the Jeep while waiting my turn to exit the parking lot. I rolled down my window and the sound was definitely not right. It was more of a clicking noise overplaying my regular dynomax rumble. Initially I thought exhaust leak. I decided to see what happened when gassed it in neutral, seemed alright and around 3k RPM it sounded normal. I pulled out of the parking lot onto the road and that's when the check engine light hit me and a loss of power kicking in at ~2,200 RPMs. When overdrive kicked in, the RPMs dropped to 1,500 and the severe shake came back. Like the shaking was close to the death wobble I had when my OEM rear trackbar mount break on me. I stopped at the next stop light and the check engine light disappeared but the low rough idle returned. Light changed, accelerated, lack of power. Hit 2,200 RPMs check engine light came back until the next light. I limped it to my local O'Reilys and used their trouble code scanner to read the code, even without the check engine light on. P0302. Cylinder 2 Misfire. They printed out a list of possible fixes(pictured below)... I was unable to look at the Jeep since getting home and plan to take a peek tomorrow in the daylight and warmer temps.

I'm wondering if anyone has experienced the cylinder misfire on a pre-2012/non-penstar engine and what their fix was? I'm worried I'm going to spend a lot of money chasing my tail on this. I can manage the easy things like checking/replacing the spark plugs and even possibly changing a coil pack if I can find a how to. But getting into the fuel lines that will require a trip to a certified mechanic. On that note, do those fuel cleaners you pour into your gas tank work worth a damn or would that be a waste of $$ and time?

Below is a print out O'Reily's gave me with potential fixes. Deep down I'm hoping the engine is toast and I will 'need' to get the LS swap.

If you can find the time, you can figure this one out. Like you said start with the easiest first. Check the plug and wire. If you have a volt meter or even better meter that reads peak voltage see what you're getting at the plug compared to others-- easiest to do with a plug tester attached to the plug. To cover fuel issues, you mentioned fuel additive, I love seafoam it works like a dream.

Before you go spends tons of money of try flashing your computer. Others may have more to add on this but seems like that's also an option if it's a deeper rooted electrical issue

I have a 13 but I can definitely vouch that you probably have a bad cylinder head because when my CEl came on those are the EXACT symptoms I was experiencing. I really hope it's more simple than that though. That's why I won't buy a used vehicle anymore. Ya never know how the prior owners have truly abused them.

Could be a cracked plug. This happened to me twice. In the dark I could see the spark and hear it. I went through a couple of different cylinder misfires before the the worst one happened.
Cylinder 3 misfire - the tip of the spark plug was broken off. The ultimate cause of this was spun crank bearings which caused the piston to hit the plug. Needless to say the engine was trashed. This was caused by a low oil pressure issue.

JeepinLife said:

If you can find the time, you can figure this one out. Like you said start with the easiest first. Check the plug and wire. If you have a volt meter or even better meter that reads peak voltage see what you're getting at the plug compared to others-- easiest to do with a plug tester attached to the plug. To cover fuel issues, you mentioned fuel additive, I love seafoam it works like a dream.

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OK, I will pick up some seafoam in the morning. I wonder if an Autozone or O'Reily's will have a volt meter and can assist?

JeepinLife said:

Before you go spends tons of money of try flashing your computer. Others may have more to add on this but seems like that's also an option if it's a deeper rooted electrical issue

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Good point, I am ProCal'd. I can try reseting.

Moochie said:

Could be a cracked plug. This happened to me twice. In the dark I could see the spark and hear it. I went through a couple of different cylinder misfires before the the worst one happened.
Cylinder 3 misfire - the tip of the spark plug was broken off. The ultimate cause of this was spun crank bearings which caused the piston to hit the plug. Needless to say the engine was trashed. This was caused by a low oil pressure issue.

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I'll take a look at the plugs in the morning. Could you see the sparks while it was running or only during startup?

LoPo said:

I'll take a look at the plugs in the morning. Could you see the sparks while it was running or only during startup?

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When it was running. The plug was grounding out to the block. Hairline crack in the insulator.

Pulled the plug for cylinder 2. I don't see any visible cracks. It's pretty dirty and looks like there is oil on it. I'm not sure if that's normal.


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Verified that the liquid on the plug isn't gas, my guess is it is in fact oil. Another angle lighting of the plug below. I've heard that's the worst case between the two and that a Compression and Leak down test is the next step in determining what's wrong. :grayno:

I probably won't be able to get it into a shop until after the New Year. Sweet.

If anyone has another suggestion that I can test/look at prior to getting it into a mechanic, let me know.

Thanks for the suggestions thus far.

Have you tried a new plug yet?

Moochie said:

Have you tried a new plug yet?

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No, but I can before taking it to a mechanic. Since there appears to be oil on the plug, I was given advice to take it in for the Compression and Leak Down test by someone that knows engines way better than I, but I will certainly swap in a new plug first. :thumb:

How much oil?

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Moochie said:

Have you tried a new plug yet?

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Tried a new plug.

No change.


Also I noticed that the exhaust seems to be... not sure how to describe. More potent.

TheDuff said:

How much oil?

Sent from my LG-D800 using WAYALIFE mobile app

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enough that the white part of the plug seems to be permanently brown. Fired up for maybe 2 mins to pull it into the garage from the street. That was enough to make it glisten when I pulled it again. I had wiped it down before reinserting it earlier.

Any coloration to the exhaust gases? Could be an issue with the valves or piston rings. Loosing compression on that cylinder and allowing oil to enter the cylinder. Let us know what the compression test shows.

If I am not mistaken, I believe it is related to your Teraflex LA kit. :cheesy:

This sucks man. Let me know if there is anything I can do to help. I know a good mechanic in Sparks if you don't have someone to take it to. :yup:

MTG said:

If I am not mistaken, I believe it is related to your Teraflex LA kit. :cheesy:

This sucks man. Let me know if there is anything I can do to help. I know a good mechanic in Sparks if you don't have someone to take it to. :yup:

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:cheesy::cheesy: Good point! I'll use it as an excuse to the wife to replace with the EVO LA kit.

Mechanic or overpriced welder? :cheesy:

LoPo said:

:cheesy::cheesy: Good point! I'll use it as an excuse to the wife to replace with the EVO LA kit.

Mechanic or overpriced welder? :cheesy:

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I've got a bead on an overpriced welder too. Oh wait, you know them. :cheesy:

No really, I do have a good honest mechanic.

MTG said:

I've got a bead on an overpriced welder too. Oh wait, you know them. :cheesy:

No really, I do have a good honest mechanic.

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Email me the info. I'm going to call a couple of places and talk this out with them. Thanks.

Leak-down tester - $64

http://www.amazon.com/OTC-5609-Cyli...d=1387827875&sr=8-1&keywords=leak-down+tester

+ 2 hours of your time

http://engineguy.com/news/engine-leakdown/

And you've got a self-diagnosis. You might want to bring it indoors first