alsur

Hey guys. I'm probably the millionth person to come here with this problem but I've researched and cant seem to find someone with the same problem as me.

Basically I had misfiring issues with my 2012 ecoboost and after doing a bit of research I had my mechanic swap out all sparkplugs with the new NGK's and he also replaced a coil that was defective. After replacing them all I still had issues with misfiring so I brought it back. He had found carbon tracking on the new plug and noticed another coil had failed. Still after replacing all this I still have issues with misfiring and I checked my plugs and one had carbon tracing on it.

Basically what I'm wondering is what would cause brand new spark plugs to have carbon tracing or am I looking at the problem completely wrong?

Thank you in advance!