Ask The Expert- Check Engine Light on my Wrangler Unlimited LJ 2004 - 4.0

Kashmir

Jeep Newb
I had issues this past weekend with a long highway trip with my 2004 Unlimited LJ. It has the inline 4.0 six cylinder. Check engine light came on after about three hours of highway speed driving and 90 degree weather. Once I got to my destination, and the Jeep cooled down ( not any temperature issues ), it started right up and seem to be fine. Drive home on Sunday, same issues with loss of power. Check engine light has been on the whole time as I had not gone anywhere to read the codes and reset.

Anyway, after stopping in my auto parts shop and reading the codes - P0300, P0301, P0304, P0306. Reset and light is off - couple of short trip near the house and no issues or light coming back on. I remember this on my other LJ, and think it has to do with plug wires and or heat shielding. Can I get any suggestions or remedies? The codes are cylinder misfires. Thanks, Phil
 
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Pthorpe84

Moderator
Staff member
I would pull your plugs to start with. There could be one failing. Just a thought.


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Cloaked Willys

Jeep Fanatic
Unfortunately this is a fairly common issue on the late 4.0L. The sensor that is where the distributor should be tends to go bad and cause misfire issues along with coil packs going bad. We have been down this road a few times over the years.
 

Cloaked Willys

Jeep Fanatic
Yeah, If you do a search for " Tj camshaft sensor issues" there are a lot of posts about it. It is the weak point of that motor.
 

Jblackhwt

Jeep Newb
I had something similar. I had to wrap the fuel rails with a heat tape. I was getting a vapor lock and having a misfire.
 
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