Hi everyone, I have a 2008 manual jeep wrangler. I have been having a misfire in cylinder 5 for a few months now and can't seem to find the fix. We started with replacing all the o2 sensors(because they were all out), spark plugs and wires. That didn't work so then we changed the fuel injectors still misfires after that. Last week we changed the coil pack but still no luck. Here lately it will normally only misfire when its cold and first time going into third gear. It feels like its just bogging down and then when it catched it takes off. Has anyone ever had this issue or have any suggestions on what we can do next to try to solve this mystery?
This is all the current codes that are on there after everything has been done: P0057, P0037, P0051, P0032, P0305, P0300, P0456, C123F, C1015, C100A, C2100, B1634, B1630, B162C, B1638, U0184, B1640 ( I know that some of these is because i have aftermarket things)

 

Since it sounds like you have an issue with a specific cylinder, have you done a compression test or a leak down test?

 

I have not done a Compression test, but I believe this my be my issue... just got it fixed and going to take it on a test run. This is the line that connects to the fuel rail that then connects to the fuel line.

 

Good possible.. keep the forum updated .. if correct many others could benefit.. BTW.. a year back another poster on a forum eventually found a ground broken on or near the fuel rails. I can't find the post but I recall the topic and his fix.

 

UPDATE...
Well guys that was not the fix... but at least I found that and got it fixed so it won't be an issue down the road. I did plug my reader backup and deleted all the codes and drove it around to see if anything changed after I fixed the line. It is still reading cylinder 5 misfire so i guess my only option now is to do a compression test on it, unless yall have any other options.

 

Well, that sure wasn't helping anything and needed to be replaced regardless. Can you clarify, are you having an issue with #5 on a regular basis or only in those two specific situations, and are you having multiple cylinders misfire in those situations (cold start and shifting into 3rd)? I've never dealt with that 3.8L personally, and looking at videos of things it's interesting how different that top end is from the 3.6L. I think if that were mine I'd proceed with both a compression test and leak down test (compression test won't identify a cracked head). I'm not even sure if that 3.8L ever had common head issues like the 3.6L but those tests are easy and non-intrusive to perform and you have already hit all the common replacements (plugs, wires, coils, o2 sensors, injectors, etc), and I sense the issue is primarily isolated to #5.

If you do those tests and observe abnormalities then you're going to be digging further into the top end. Digging around a bit it looks like burnt exhaust valves are a common issue on that 3.8L. I think I'd try to eliminate anything and everything that is easy/accessible before digging further, but you're getting to the end of that line.

@Sixty4x4 - do you have any thought on this?

Also, Ronjenx has a factory manual checklist of misfire diagnostics. This thread could be a good read -

https://www.jk-forum.com/forums/stoc...9/#post4052691

If we are indeed talking #5 is the specific issue, need to think through the things that could affect #5 while not really affecting the others.