Hey Guys,

I’ve been working on 2015 Jeep Cherokee 2.4L.

Got P0303, P0304 misfires

Started from a missing gas cap (P0457 P0456).

Got the “vaper leak pump” - Installed - No more codes - Fixed.

Then Got P0303 & P0304 problems, so I got new spark plugs hoping that

would fix the problem and they haven’t been changed in a long time.

Took plastic cover off found oil on top of valve cover. Maybe that's my problem.
I figured it was valve cover gasket to be replaced.
So I replaced All gaskets for valve cover, spark plug tubes and bolts.

Started it up, still hear compression problem (rough idle), but, only

Code P0303 - 3rd cylinder misfire. Someone said, check coils, move them around.
So I swapped #3 coil and put to #1 coil etc. And got now got a P0303 and P0301.

Some say it could be lifters and/or rockers… Did not see any rockers off or broken, but I do see some wear on the camshaft.
I looks black on the camshaft, where cylinder #3 would be. Some on #2.

Enclosed is upclose picture… Do you think it’s a lifter issue from the picture?

 

so if you had code p0303 and p0304 and then you swapped the coil from cylinder 3 with cylinder one and then you get p0303 and p0301 then you have a bad coil. just replace them all since they also need to be replaced at 80k to 100k.

did you check that the gap on the spark plugs to make sure they were correctly gaped before you installed them? regardless if they are pre-gaped. did any of the spark plugs have oil in the electrodes or tips?

camshaft wear is normal as long as it's not severe as you have two metal parts gliding over each other. you will need to check the specs to see if actually the cause. or check your compression on all the cylinders.

 

Thanks for feedback. New spark plugs have .043 gap. Good to hear 'normal' wear on shaft, cause I just watch a video on how to take the lifters and rockers out from under camshaft.
These guys took the engine out and had to remove serpentine belt, pullys water pump, timing case, timing chain just to get to the camshaft and take brackets off shaft to get to lifters and rockers.
I hope thats not the problem.

I've also seen plenty of videos where the new coils didn't work, so I don't know but replacing them after 100k is needed.
Thanks.

 

it's rare that the camshafts or rockers are too worn down to cause a misfire. you literally have to run it with very little oil for a good amount of time.

 

Quick Update: I bought a new coil for cylinder 3 did not help. Tested it on cylinder 1 same errors. Did compression test each cylinder and all 4 are the same and robust, which is great because I thought it might be head gasket, so that's not it.
Scanner did not pick up any vacuum leaks, so I'm at a lost...still. I wish there was a way to 'reboot' the system like a computer and start over.

 

Bdhs