Intake Manifold Carbon Build Up?

[olddog]

I do not believe it is oil. It is dry carbon, just like you find in an exhaust manifold. A hair oily right by the PCV port, as you would expect, but the rest is dry.

I do understand the MAF cleaning.

[FWB]

if no fuel is running thru there......if an air cleaner is on the throttle body

if your neighbors cat isn't defecating into there

what else would it be?

you would have to have one hell of a cam overlap to push oil up from the bottom, coupled with a crappy ring seal


when the oil hits a hot surface it cooks and gets hard.