I just acquired a 2013 Ram truck with a 5.7 hemi. The check engine light is on, code is a misfire on cylinder 7 (p0307).

I bought a pair of plugs and a new coil, figured that would likely solve it. When I removed the existing plugs from the engine cylinder 7 the rear one was ok looking, but the front spark plug was caked completely with a hard clump of sandy gritty oil. I have never seen anything like it, it was a big hard crust over the entire gap end, clearly it couldn't fire, but it was so strange to see such a build up on a plug. I never seen anything like it before.

Anyways, I replaced the 2 plugs, and the coil pack, erased the engine code, restarted it and it still idled rough and threw the same code again.

So my amateur guess is that the same crust of shit that was on the plug is on the injector and/or the valves. I have no idea what causes so much build up or what the simplest solution is.

Am I wasting my time trying an additive like seafoam into the cylinder to soak? Should I just pull the head and see if the #7 valves are all crusty with the same tar?

Thanks to anyone who can explain how the hell out got so crusty and what I should try to solve it.

I'm moderately handy, not afraid to try and learn, and have a gnarly set of tools. So I will try whatever is recommended.

Thanks.