is it normal for the TB and UIM to be black and oily inside?
 

:Wconfused

We are tearing down the long block since nothing is making sense. While pressure checking the UIM/TB in isolation, I noticed the inside of both is coated with black oily substance. almost like a thin coat of grease with graphite mixed in.

Is this normal?

never seen that before i know the manifold will be oily from the oil injectors but a thin coat of a greasy substance.. i have know clue. that's the only thing i can think of that would make the manifold oily is the injectors but the throttle body i have no clue on. doesn't sound normal at all though.

if i remember right there is a vac line that sucks the air build up out of the oil system and returns it through the intake .

Yes it is pretty normal in moderation. If there is sludgy buildup you need to clean it. The OMP lines and everything run around there.

Yes it's normal, but has nothing to do with the OMP. the PCV system (or rotary equivalent) takes the overflow of oil and vents it into the intake right behind the AFM. this makes everything from the AFM back get oily and gross. it won't hurt to clean it though.

sea-foam time