First time writer long time reader. The other day my wife's jeep through a misfire code for cylinder #5. So I started by changing the spark plugs. I bought some cheap spark plugs because the part store did not have any of the recommended spark plugs available (which are champions) I replaced 1,3 & 5 because i was in a parking lot. Misfire still there. Got it home and bought 6 new champion spark plugs and replace all 6 of the and the misfire still there. I went ahead and replaced coil packs on all 6 cylinder and the misfire is still there. I tested the fuel injectors 2 of them tested bad compared to the other 4. On cylinder 2 it ohmed out to .21 and on cylinder 6 it ohmed out to .002 while the other 4 injectors ohmed out to .142 . I went ahead and replaced all 6 injectors. Guess what cylinder # 5 misfire is still there and yes you can feel the misfire. I took the valve covers off to check out the rocker arms and to make sure none of the intake or exhaust valves where stuck. All of that looked great no broken springs and all the rockers are in place. Ive looked up multiple possibilities and I'm stuck. So that's why I'm here and if anyone can give me some other direction to head I would be greatly appreciative. Oh I also have 4 new 02 sensors imma try when I get a chance. Thanks
2017 Jeep Wrangler Sahara cylinder 5 misfire
- Thread starter lopsidedmarsh
- Start date
I can’t remember but this might be similar to an issue @WestCoastDan had. Maybe he can chime in, he spent a lot of time getting his fixed. Ended up being some bad wires in the harness. I am just not sure it was the exact same issue.
Yep, what I was thinking. I think his was injector wiring... I'm sure he'll chime in.
WestCoastDan
JK Enthusiast
First, I'll start by saying that while my efforts (and results) might suggest that I possess unique or expert knowledge on the subject, I'll admit to just being mechanically inclined and determined not to spend needlessly for a professional tech to do the same things that I can accomplish myself for free at home.
I'm also humbled by the apparent confidence others have in my abilities.
Now onto the problem.
I actually couldn't find the post that I was looking for, but this is the crib-note version of what I went through:
https://wranglerjkforum.net/threads/jk-going-into-worse-than-limp-mode.32306/post-467430
In an effort to find a resolution, I understand that you have already;
- replaced plugs
- replaced coil packs
- replaced injectors
Misfire code and condition remains on #5.
You are now contemplating replacing the O2 sensors.
I'm not sure how O2 sensors could cause a single cylinder to misfire, but remember; I'm no expert.
If I were looking for the root cause of a #5 misfire, and I had already replaced all of the above, it would make sense to ensure that the injector harness and/or connector isn’t to blame.
During my troubleshooting and repair, I discovered multiple injector connectors that were brittle and falling apart.
There were 2 with damaged locking clips, so they could not be reused.
I ended up replacing all 6 of them with these:
https://www.ebay.com/itm/2555053204...pid=5337789113&customid=&toolid=10001&mkevt=1
I also found a damaged coil connector, which I replaced with this:
https://www.ebay.com/itm/3646870500...pid=5337789113&customid=&toolid=10001&mkevt=1
(I only found 1 of these to be damaged, so I only replaced the one.)
The root of my issue was this connector at the oil pressure sensor:
https://www.ebay.com/itm/3631084514...pid=5337789113&customid=&toolid=10001&mkevt=1
While replacing all of these connectors with the harness still in the Jeep was a genuine pain in the ass, it solved my issues.
(If I were doing this again, I would either just replace the harness entirely, or at least remove it from the vehicle first.)
If you are not comfortable splicing into your harness, you could opt to replace this portion.
Here's a used one listed on ebay:
https://www.ebay.com/itm/1351708952...pid=5337789113&customid=&toolid=10001&mkevt=1
(I have no affiliation to this listing, I just used it for reference)
I just found a new one as well, which is probably a safer option:
https://www.moparpartsgiant.com/parts/mopar-wiring-injector~68087837ac.html
I'm also humbled by the apparent confidence others have in my abilities.
Now onto the problem.
I actually couldn't find the post that I was looking for, but this is the crib-note version of what I went through:
https://wranglerjkforum.net/threads/jk-going-into-worse-than-limp-mode.32306/post-467430
In an effort to find a resolution, I understand that you have already;
- replaced plugs
- replaced coil packs
- replaced injectors
Misfire code and condition remains on #5.
You are now contemplating replacing the O2 sensors.
I'm not sure how O2 sensors could cause a single cylinder to misfire, but remember; I'm no expert.
If I were looking for the root cause of a #5 misfire, and I had already replaced all of the above, it would make sense to ensure that the injector harness and/or connector isn’t to blame.
During my troubleshooting and repair, I discovered multiple injector connectors that were brittle and falling apart.
There were 2 with damaged locking clips, so they could not be reused.
I ended up replacing all 6 of them with these:
https://www.ebay.com/itm/2555053204...pid=5337789113&customid=&toolid=10001&mkevt=1
I also found a damaged coil connector, which I replaced with this:
https://www.ebay.com/itm/3646870500...pid=5337789113&customid=&toolid=10001&mkevt=1
(I only found 1 of these to be damaged, so I only replaced the one.)
The root of my issue was this connector at the oil pressure sensor:
https://www.ebay.com/itm/3631084514...pid=5337789113&customid=&toolid=10001&mkevt=1
While replacing all of these connectors with the harness still in the Jeep was a genuine pain in the ass, it solved my issues.
(If I were doing this again, I would either just replace the harness entirely, or at least remove it from the vehicle first.)
If you are not comfortable splicing into your harness, you could opt to replace this portion.
Here's a used one listed on ebay:
https://www.ebay.com/itm/1351708952...pid=5337789113&customid=&toolid=10001&mkevt=1
(I have no affiliation to this listing, I just used it for reference)
I just found a new one as well, which is probably a safer option:
https://www.moparpartsgiant.com/parts/mopar-wiring-injector~68087837ac.html
This site contains affiliate links for which Jeep Wrangler JK Forum may be compensated.
Thank you @WestCoastDan this is what helps us to get better. I suspect most of us are just shade tree mechanically inclined people.
@Chris I am wondering if there is way to get this in the resources section or something. I am not sure how much time @WestCoastDan spent trying to find the old post but there is certainly great information in this and how to possibly fix a misfire issue.
This site contains affiliate links for which Jeep Wrangler JK Forum may be compensated.
Thanks man! Yeah I inspected some of the wires just mainly around cylinder 5 though. When I get some time I'll do a deeper look through on them. Right now I do have the wiring harness basically half way out. I unplugged everything to move that dang thing out the way.
I was looking into replacing the 02 sensors since they determine the air-fuel ratio figured why not since I've replaced this much we'll see though.
I really do appreciate the input and like I said when I get some time imma dive back into it and see what happens.
This site contains affiliate links for which Jeep Wrangler JK Forum may be compensated.
What I do if I find a Post that's important is to bookmark that Post then I can look at my Bookmarks to see if there is one that might help later. If I could figure out how to move that Post i'd do it, but i'll work on it.
WestCoastDan
JK Enthusiast
The posts about my repair journey are somewhere in the "what did you do to your JK today" thread. There are just so many that it was difficult to track down the specific one that I was looking for.
I Bookmark posts that i find relevant or interesting to me, but I don't bookmark my own.
I Bookmark posts that i find relevant or interesting to me, but I don't bookmark my own.
I remember seeing them and I looked there but couldn't find them, when you have something like that it's better to have a Thread about it instead of in the WDYDTYJK Thread. If you happen to find it again give me the Post numbers, and when I get time i'll look again.
I’ve started doing the same thing about bookmarking post. Makes it a little easier.
WestCoastDan
JK Enthusiast
I just happened to locate the post I was trying to reference above...
https://wranglerjkforum.net/threads/limp-mode.32181/post-466190
https://wranglerjkforum.net/threads/limp-mode.32181/post-466190
Alright. So I inspected the whole wiring harness didn't see any nicks or bare copper showing. I did a compression test and had no compression on cylinder 5. Checked out the lifters and rocker arms. I had a bad bearing on one of the rocker arm on the intake side of cylinder 5. I went ahead and replaced the lifter and rockers on cylinder 5.. put it all back together and no change. So far I've done spark plugs, coil packs, injectors, lifters, rocker arms & inspected the whole wiring harness ..
Maybe your spark plug fouled out on cyl. 5 since it had a problem with that cylinder.
Well it took me a while to get back to looking at this thing I figured something was going on internally and I decided to pull the head and exhaust valve on #5 was cracked! I went ahead and replaced all the exhaust and intakes valves and put everything back together and it runs and drives great! Don't really know how it cracked, maybe some crud inside the exhaust manifold fell off and wedge behind it? But the cylinder walls and top of the piston looked great. There was no damage to them.