Skimonster

First time posting but I'm out of solutions. CEL p0306 has been on for some time. The first thing I did was put a fuel additive (seafoam) in the gas and it went away. After a period of several days it came back. So I've been going on the list of solutions here's what I've done:
Replaced plugs
Replaced boot #6
Replaced injector #6
Replaced O2 sensor

It keeps coming back. At this point I don't understand why it goes away with a fuel additive or what to do next. I haven't done a fuel pump pressure test or a compression test. My main question is why does the gas additive work to turn off the CEL?

Sv_dude

This is purely a guess but I’d assume that if an additive will clear a misfire code then I think your valves are not seating well and the additive cleaned some of the carbon build up. You could also be at an early stage of head/valve failure. I’ve had a p0304 for about 3 years and have ignored it since the Jeep drove well and compression tests were within spec.

Do a YouTube search for seafoam, there’s a good video by a channel called jkgearandgadgets. He explains how to do seafoam through an intake vacuum line off of the brake booster. That may help you out in doing a good cleaning of the cylinders and head.

Skimonster

That's what I'm worried of is this is a bigger issue. Like you said it runs well but I feel like this could soon spiral. I was using seafoam in the gas and it helped so maybe the cleaning is a good option. I'll try that. Thanks

Jay2013jk

Update the forum if you try this .. might help .. will be interesting to read if it helped.

Skimonster

I just did the seafoam through the brake booster let it set for 15 minutes and ran it. A moderate amount of smoke came out but nothing to write home about. I dumped the rest of the seafoam in the gas which will probably keep the CEL off for the time being. In a week I will update it if it's still off and perhaps this is the solution.