I have an 01 xj throwing codes p0300, p0303, and p0304. I understand these are multiple misfires and misfires in cylinders 3 and 4. Im trying to diagnose what may be causing this.
Heres what I've done or checked so far:

I have new injectors on the way, not sure when or if ever, those have been replaced.

Wondering if it could be my o2 sensors? I had auto zone read the codes a while back and had a sheet printed up and one code had something to do with heater malfunction, can't remember what it said exactly or the code as i can't find that paper. However, I've done some reading and saw that it could be the heater element in the o2 sensors might have gone bad and it could possible throw that code? I will check tomorrow for crimped or melted wires coming from the o2 sensors. Not entirely sure this causes cal 3&4 to misfire though.

Took rad cap off and ran engine to see if coolant shot out, indicating a bad head gasket, it didn't appeared fine, no oil in the coolant or coolant in the oil.
Have yet to do a compression test, but performing as those previous tests seemed to point the other direction.

I have sea foamed the TB with their spray. Also bought the traditional sea foam and have some in the crankcase before i change the oil in the next 100 or so miles, and put the rest in my tank to help clean out the fuel system.

I have hydrolocked the engine before, and replaced coil pack, plugs, and oil immediately after. Jeep runs fine and has no sign of any issue after that, my thought is that maybe something internally has just now shown up?

Im stumped as to what this could be, I've reset the PCM hoping something would happen, and am still waiting on the 50 cycles to complete, but the CEL is still on. Ive reset the PCM before when i had a engine light on and it went off right after the reset. I have noticed what looks like a "wetness" if you will near cylinders 3 and 4 on the valve cover on the fuel rail side. Ive read in hot climates (I'm in AZ and it gets to 120 some days) that the fuel can vaporize in the fuel rail and cause this issue, might get some heat wrap and see what i can do about that.

Jeep seems to be running better than ever, so I'm not sure why these codes are on their?Is their an other way i could test for a blown head gasket or cracked case? Any ideas and/or help would be greatly appreciated!

 

sry, wrong thread....

 

Wrong thread, in an old thread. lol