Spark plug Colour
Turbo Mini Forums

Hi all, This is a question regarding my N/A fast road 998.

I'm scratching my head a little to be honest and wondered if anyone can help!

Ok, problem is one spark plug is sooty, not oily. From flywheel, second spark plug along.

All others are light brownish.

I have replaced plugs and leads and no change, don't think its a fuel issue due to other plugs being ok. Car is running fine when warm, a little miss fire when cold. I'm using a hif38 carb from metro 998 which I've just rebuilt. Don't think there is any air leaks......head gasket?

Any help guy would be great. thanks in advance.

martin

not sure mate? plug gap to big? its ether getting more fuel in the first place or its not burning it properly on that cylinder?

have you done a compression test? i don't know if a broken ring would make if not burn properly? or maby tight valve adjustment on that cylinder ?

you say its sooty not oily so i dont think its a valve guide seal sort of thing

the others should be able to give better answers than me im really just guessing mate

what manifold are you running? could be biasing fuel air mix to that valve?

Hi, I'm using an alloy inlet manifold. Plugs are BPR6ES and gaps are 0.8mm.

check the lead to that plug - could be a weak spark causing a poor burn.

Try swapping the lead and see if it makes any difference - remember to clean the plug first!