Spark Plug condition info?

[Aragorn]

ok my 16xe in the nova has never seemed quite right, idle is very lumpy and car smells quite heavily of fuel at idle

i put it on emissions tester in MOt station and co was low (0.7%) but hydrocarbons was interesting - the idle seems to drop/shudder every few seconds, almost like a missfire, totally at random and with every shudder the hydrocarbons rocketed up immediately after from around 100-200 upto 700-800 then returned to the normal value

it chucks out some black smoke if u floor it when its cold and it also seems to bog down a bit and seems a bit flat at the top even when its fully warmed up so i was thinking its possibly overfuelling and checked the plugs

its got ngk br6ek i think in it and at a quick glance they looked ok, but on closer inspection although the 2 electrodes were normal sandy brown color the core electrode seemed to have a slight greeny/yellow tinge to it and the base of the plug thread was very black

any ideas as to wether this black on the bottom of the thread is ok/normal? and what about the weird tinge...

thanks

[Stuart]

ropey coil pack.

[Riggy]

lol might sound daft but in the back of my haynes manual

the green one theres a load of pictures of sparkplugs in differerent conditions and it explains what causes each one

[Aragorn]

looking at the normal plug it seems the black deposits on the base are normal

so its just summat funny with the core

u think it could be a ropey coil pack? i was thinking my crank sensor is a bit iffy as its been knocked about a bit and ive noticed a few times at high rpm in high gear the rev counter sometimes drops back a notch and then goes back up on the digidash rev counter although there is no difference in engine noise at that time

any way to test the coil pack other than getting anothe rone and trying it?

[Stuart]

find appropriate info and test the resistance of the primary coil etc

or get another one and test with that