Hey guys, I have a 14 countryman jcw that has 120k miles. It has a low oil pressure light come on so I pulled the pan suspecting it was the guide rails coming apart and clogging the pickup screen. Sure enough that was my issue. I bought a full timing kit and timing lock tool. Everything went great on Install but I'm now getting a p0300 and p0304. I double checked timing and everything still aligns perfect. Tried new plugs and moved coils around but no difference. Car idles perfect, revs great in park and drives fine at low rpm. As soon as you try to quickly accelerate it misfires hard and shuts off injector to cylinder 4 and engine light comes on. Once I reset light it idles and runs fine until you accelerate. Not sure what could be the issue here. Id imagine it's tied to the new chain but everything appears to be correctly aligned so I don't think timing is off. Any ideas?

 

As your problem is only on one cylinder it probably isn't the timing, though of course it is possible.

Next suggestion was moving ignition coils but you already did that. The fault stayed P0304 for cylinder 4 after moving plugs/coils? I doubt this, but if you did have low oil pressure (not just the fault but actually did have low oil pressure) I assume it's possible to have had bad oiling on that cylinder and damage to cylinder wall/piston could've occurred. Compression or leak test may show something, but maybe not as it idles fine.

Is it possible you loosened a head bolt by mistake while doing timing and now it's a head gasket leak?