black substance on spark plug

[fordby4]

I changed out all the plugs two weekends ago and the #5 plug had a lot of oil and buildup on it. I found out that my lower intake manifold bolts were loose so I tightened them and the oil stopped getting in there. I put some bosch 2 platinum plugs in and I ran it for a few days. Then I looked at all the plugs again to see how they were firing and all of them were firing good except the #5 plug. It has a lot of black stuff around it that kind of looks like black ash or something. Does anyone know what I can do to get rid of that black substance?

 

[tenikiwon]

try fuel inj cleaner or higher octane fuel. Might just be something dirty.

 

[Alec]

higher octane fuel will make that worse. You need to clean your injectors or hope that just some fuel system cleaner will do the trick.

 

[tenikiwon]

I always thought higher octane and fuel injection cleaner were about the same.

 

[Alec]

Higher octane fuel in a motor that can't burn it properly will just result in more carbon buildup. Premium fuel usually does contain more detergents, but it's better to just buy a bottle of the stuff.