What's wrong with this spark plug?

[InvisiBill]

The last couple times I've changed them, I've noticed crud on my #4 plug. When the plugs get to the point of needing to be changed, I can tell. Other than that the truck runs great. After changing the plugs this last time, I did a quick 0-90 WOT run, and saw 1.6* of KR at TC lockup, flat 0 the rest of the time.

This time it seems to have some black around the edge of the threads, but for the most part it's just tan stuff on the center. It looks like sandy mud or something, light brown with a fine texture.

The truck is mostly stock. Walbro with a Racetronix harness, stock FPR, hotwired Jabsco with heater hoses. 160* stat, unplugged vac line to EGR, drop-in K&N. Any ideas on what might be causing this?

 

[jwaller]

thats absolutely nasty. do you have a head gasket leak or an IC leak....

 

[InvisiBill]

Probably? I don't know, that's why I asked...

I've seen it several times, only on #4. So of the two, I'd say head gasket. =( And yes, it's especially bad this time. I had been neglecting the Sy due to wedding stuff. I've never seen it that bad before. The other times I saw it, it was just a bit of a coating on the center, not huge gobs like that.

 

[ItsMyTy]

wow... i'd do a compression check soon...