Welp she's misfiring..

[baybaja]

My baja is giving me a p0304 code. Which I know is a cylinder 4 misfire. Idle is pretty rough, check engine light occasionally blinks which I hear is an occurring misfire, and cruise control light blinks. Just replaced the spark plugs again and my cylinder 4 plug had oil on it. Others did not. Checked all coil packs for cracks or signs of arcing. None found. Not sure what else to do guys, but I wanna drive my baja again. Help!!

[Acro2pilot]

I suggest first swapping coil packs from one cyl to the other (move 4 to 1 or similar), they do age and might look fine but are past their prime, I just replaced all four. If you swap them and the problem moves with the coil then you know you have one failing. And check your connector condition they can corrode or fail to grip in place if the plastic clip breaks. Is your Baja turbo or NA?

An oil fouled plug can cause those issues and before jumping to conclusions about the cause of the fouling perhaps a prior owner or a shop did not change that one, it happens. Without seeing your plug I have no idea how bad it is, how many miles on the truck, do you know for absolute certain if #4 was changed? First thing to do is throw in a set of good plugs (which you did), swap coil packs as I suggested above and see if the problem is eliminated or moves to another cylinder. If things behave well then pull that plug after a few thousand and have a look, also monitor oil consumption. If it oil fouls again I would suggest a compression and leakdown test and a borescope of the cylinder.

You are correct on the flashing CEL, it means a "serious" code is going on at that moment, the cruise control is Subaru's way of getting you to do something about a CEL you might ignore.

[anarchy1024]

Have the spark plug wire been replaced? I had a Voyager that was misfiring; replacing the spark plug wires fixed it.

[baybaja]

On my first oil change after purchasing my baja, btw it is turbo, I did all of the basics including the spark plug change. When I pulled the old ones out it looked like they haven't been changed at all but no oil. So just recently I replaced them again and swapped coil packs between all 4 cylinders, now it's giving me p0301, p0303, and p0304.. even worse than before!

[Acro2pilot]

Mine was running well until the last tune which upped the boost again and I got missfires on 3 out of 4 cylinders, replacing all 4 coil packs fixed the problem, they can fail as well as get weak, you may need to replace them.

[ChrisIB]

I had the same problem with cylinder one. I changed plugs and coil packs and the only thing that I got was new coils and plugs. My problem was the fuel pressure regulator. The circuit was stuck on hence a richer fuel mix. Everything you described sounds like it's running rich.