Ignition Misfire, Or Something Else?

[sonicz]

It absolutely can be your injectors either blocked up or playing up as has been pointed out. Your logic of ruling them out doesn't make sense. Mine looked exactly like that when I had injector troubles from running on e85. One or two lean and white the others black. What fuel are you using?

[harks]

98 ron.

i guess i had ruled them out thinking it was all down to a coil problem, which evidently is not the case! ill inspect them later in the week.

[sonicz]

Well yea it could be a coil problem as well, not igniting the fuel and thus running overly rich and black, but it could be an injector overfueling totally messing with the AFR and causing the same symptoms. So why not make it easy and start the process of elimination with the easier set of variables first. Borrow a known working set of coils and see how you go.

Alternatively why don't you move the coil pack that causes the "white" spark plug tip to another cylinder, clean the plugs and see if the white spark plug moves location with the coil pack of stays in the same cylinder. If it moves its mostly likely a coil issue, if it stays its most likely an injector issue.