Plug #6 Sludge

[Moozak]

Was trouble shooting a loss of power issue and when I pulled the plugs, #6 looked like this:



The others were looked grey-ish brown:



I cleaned it up and put it back in and now the power is back to normal. No 6 cylinder was not firing at all I suspect.

What was the cause of this? Why just #6 I wonder?
Thanks for any input, I will monitor the plugs more regularly,

Jon

[db_cooper]

If this is on your 77 911..could be the CIS injectors..#6 is not atomizing the fuel very well. Of course it could be a spark plug wire with high resistance too.

Once a spark plug fouls..they get very sludgy like your picture. Any imperfections will foul a spark plug.

I would suggest new plugs (I like NGK myself) and then run it for a few hundred miles and remove..see what you have then.

[Jerome74911S]

I have a comparable situation, but not as bad as yours. My #2 plug blackens up, while the others all remain nice and clean. I put in a new injector - same fouling on #2. The spark plug wires are new (Beru OE), as is the distributor cap. Dizzy has Pertronix.

I am guessing that I have some tiny leakage from the oil seal on the top of a #2 cylinder valve guide.

Therefore, I installed a one-number hotter plug into #2 to see if that burns off whatever is causing that dirty plug.

[Moozak]

Thanks for the replies. Yes, this is for my 77 911 CIS. I recently replaced all of the injectors with new ones, but I will double check the spray pattern. I have been going through quite a bit of oil, so I think it's possibly a valve guide or rings... I'll order some new plugs and monitor the situation. I'll add some fuel additive as well to see if it clears up some of the carbon sludge.

[Dan J]

That's oil fouling A leakdown test would be appropriate