carbon covered spark plug

[roulli]

good evening,

when I changed my 4 electrode Beru's vs. new NGK, I noticed that plug from cylinder 6 was black. After two days driving with the NGK, I checked, and it was again plug from cylinder 6 that is black. I have to say, that I checked always after I parked the S3C into the garage, which is not without manoeuvering, ideling, while opening the door and so on...
All the other plugs were however totally clean.

Does this mean, that the injector of cylinder 6 is knackered?

Cheers
Patrick

[HarryW]

quote:good evening,

Does this mean, that the injector of cylinder 6 is knackered?

Cheers
Patrick

Possibly, sooty black or wet black?

Could be weak spark = dodgy lead/heat cap thingy
Could be too rich = injector not closing properly on No6
Could be oil = valve stems passing oil
Could be ????

Easiest to diagnose would be a dodgy lead or that heat cap/adapter thingy, by substitution.
I hope this helps.

Harry

[roulli]

Thanks a lot Harry,

Will follow your roadmap. BTW the leads, cap and finger are all new from Motorcraft. But this is no guarantee...
Cheers Patrick

[roulli]

If injector No. 6 would not close completely, I should maybe add an Injector Cleaner to the next refuel.
I wonder however, if this might not harm the cats?
Thanks for any comment.
Patrick

[johno]

quote:
If injector No. 6 would not close completely, I should maybe add an Injector Cleaner to the next refuel.
I wonder however, if this might not harm the cats?
Thanks for any comment.
Patrick

If your exhaust valve clearance is incorrect this can also cause the hole combustion chamber and therefor the plug to 'blacken' aswell. May be worth double checking them as it only on one cylinder.

Cheers

Mark

[roulli]

Thanks Mark,

as my S has got hydr. tappets, valve clearance should be ok.

Cheers Patrick