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JK 3.8 intermittent missfire

3K views 15 replies 6 participants last post by  GreenRubi 
#1 ·
Hi ,
I am having this odd problem with my JK 2008, It's hesitate and stumble after few mins of startup and will lose power + flashing check engine light for a minute or 2/then it will drive just fine until I turned the engine off.
I am getting codes :
P0300 multiple miss fire.
P0052 its O2 sensor related
P0158 another O2 sensor code.
Already changed driver side O2 sensors, sparkplugs, wire set, coil pack and Crank position sensor also my PCM was replaced few months ago.

I am really tired of this madness my stealership didn't know what's the cause they reset codes and say it's fixed and after few mins problems are back again.
 
#12 ·
Cat converter might cost around 600-700$ and that is a lot.
I might look in junkyards for one.
Out of a low mileage jk.
I also think both of my exhaust manifolds are cracked I will take a closer look.
If then I will just grab a set of doorman's manifolds.
But will try to clean egr first and see if it will fix it.
 
#14 ·
So my check engine light is now out and my Jeep seems to be running fine. I have not changed anything yet. It has been dry out and I'm wondering if something just got wet. Would a CAT converter come and go like this? Shouldn't this problem be permanent if my CATs were bad?
 
#16 ·
I bought my 2008 JK used four years ago with 18k on it. It now has 31k on it and it has done this (stumbles with low power upon acceleration for about 2-3 mins after first being started in the morning) as long as I can remember, but it has never thrown a code. Once it warms up it is fine.

I always chalked it up to the 3.8L being cold natured. Perhaps some other 3.8L JK owners can chime in and let us know if they have experienced the same thing.
 
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