Need help with P0304 misfire

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Blue16Rubi

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Joined
Jun 3, 2023
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Ok this is going to be a long one so bear with me... I have a '16 Rubicon Hard Rock with just under 60,000 on it. Automatic. Babied, regular oil changes. About 16 months ago, my CEL came on and I got a cylinder 4 misfire code, P0304. Absolutely no symptoms whatsoever. Took it right to my local garage and they replaced plugs, an ignition coil, spark plug boot, and intake manifiold gaskets. Got it back, no issues, all was good. About 10 months later, CEL came back on, same P0304 code. No other codes, no symptoms. CEL was intermittent, coming on randomly then disappearing for a month or two at a time. Jeep runs like a champ this entire time. A couple of moths ago it suddenly started idling rough. Rough in park, rough at stop lights and such, but smoothes right out beyond that. Checked codes again, still had the P0304 but also had a P2198. Changed out the corresponding O2 sensor and while the P2198 code went away, the rough idle didn't. The motor was shaking pretty good and you could really feel it in the steering wheel. Since then, i have changed plugs again (used Bosch), the ignition coil in #4, the fuel injector in #4, ran the gas out, seafoamed it, new gas. Took the valve cover off and everything looks perfect under there. Compression test gave me about 140 on #4, higher on #2 and #6 though. The rough idle is still there, but I don't feel it in the steering wheel or see it in the motor now, it's like it's all behind me in the exhaust. No overheating, no fluids leaking, oil pressure and levels are where they should be. Oil looks good. No ticking or knocking. No loss of power. Once in a while it it hesitates to start, but has never stalled. Sometimes the P2198 code is present, and a couple of times it's also thrown a second O2 sensor code (I don't have it in front of me right now, I'll update with it). Today my CEL started flashing. Was going to do a leak down test today but probably won't have the time to get to it.
Only other thing going on is a bad front wheel speed sensor which I'm assuming can;t cause the CEL to flash?
Anyone have any advice?
 
Does it burn oil on start-ups? I'm asking because if there is an exhaust valve leak it stands to reason there may be some white smoke coming from the exhaust on start-up.
 
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Chris said:
Does it burn oil on start-ups? I'm asking because if there is an exhaust valve leak it stands to reason there may be some white smoke coming from the exhaust on start-up.
Click to expand...
So I thought maybe there was when it was cold out, but I wasn;t 100% sold on it. Now that it's warm, there is absolutely no smoke. And for what it's worth, I've been checking my oil often, level is completely consistent.
 
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