If you have carbon tracking on the spark plug, it is also on the plug wire or coil boot depending on the style your ignition system is setup. If you only replace the spark plug, that mark thats on the plug wire/boot will easily form on the new spark plug & cause it to misfire again within weeks or so
Change the plug first. If that doesn't solve the problem then wires and coil. If that doesn't work, then do a compression test
If you had listed the year make and model of your car we could study your ignition system and help you out.
It's not the spark plug 95% of the time, check the coil / coil pack, plug wire, and injector for that cylinder.
I checked the message with my computer and it shows #7 is misfiring. The light started to blink then came back on and now off. Not back on yet. Should I still change the plug or the coil too? I just changed the plugs a yr ago and one went out. Is this a poss coil issue too? Thx
