Multiple codes and cyl #5 misfire

[David Vachon]

I have a 2012 Liberty that started with poor acceleration / power and misfires on a recent camping trip. limped home and pulled codes P0305, P2305 and P2308. I swapped around all the plugs and coils hoping to find that it would change the cyl misfire but no dice. Not sure where to start investigating from here, I'm pretty handy but not all that engine savvy. Thanks in advance!

 

[LibertyTC]

Welcome to the forum.
Make sure you have the correct spark plugs in there and that the gap is correct.
Refer to KK owners manual, ZFR6F-11G (Gap 0.043 in [1.1 mm] are the correct ones.
Cylinder # 5 is misfire and the coil pack code is also present.
Get a new Mopar Coil pack and spark plug in on cyl #5. Hopefully That cures the problem.

 

[David Vachon]

Any thoughts on why I would continue to get a misfire on #5 even after swapping the coil packs around? The plugs are NGK, looked fine when I pulled them. Also, not sure if this would be of interest, the dealership just replaced both cylinder heads about 2 mos ago, found that the drivers side was warped and was dumping coolant into #5. Funny that this same cylinder is now misfiring... Finally, after looking around online I found what I believe to be the correct cylinder designation but want to be sure I'm correct.

6 5
4 3
2 1

Thanks for your speedy reply!

 

[LibertyTC]

Without the 2012 Factory service manual, I can not confirm the firing order, dealer should have the info handy/ accurate.
Since the dealer did the cyl heads work 2 months ago, I think I would want to tell them whats going on, and let them diagnose further.
Cylinder leak down test, and compression should be checked for sure.

 

[David Vachon]

So, I took it to the local dealership and they diagnosed it as needing a tune up, kinda strange since moving around the coil packs didn't have any effect on what cylinder was misfiring. I trusted them and did the tune up, it worked! all the misfire codes cleared up but now, I'm getting a P0420 code for the catalytic converter. Great... Any thoughts on how I should proceed? Should I pull the O2 sensors and clean them, see if the code clears up? Should I just fork over the $100 plus dollars for the dealership to diagnose it? My fear is that with all the problems (the cylyner head warping and dumping coolant into cyl #5, then the misfire problem) I have a clogged catalytic converter. Would love to hear from someone with experience with this code.

 

[John P.]

I would clean/replace the sensors first and then see what happens. They probably did a complete intake cleaning on it that could have affected the sensors. If you have a scan tool that lets you view live data you could rule out the cat possibly by watching how bank one (upstream) and bank 2 (downstream) behaves. My 2 cents