What would cause black soot in the throttle body?

[Vince13]

Pulled the up pipe off the throttle body today and the throttle blade and throat have a heavy layer of black soot. The engine has about 500 miles on a fresh rebuild. The deposit isn't oily and will only wipe off with carb cleaner.

I have recently been chasing a cold start issue and had pulled the up pipe to remove and check the IAC valve.

Is my turbo taking a dump?

Thanks

 

[TurboBuRick]

Sounds like oil deposits. Do you still have the breather tube from the passenger valve cover to the turbo inlet ? That will put oil in the intake. Turbo seal could be another cause.

 

[RmvBfrFlght]

Pulled the up pipe off the throttle body today and the throttle blade and throat have a heavy layer of black soot. The engine has about 500 miles on a fresh rebuild. The deposit isn't oily and will only wipe off with carb cleaner.
Thanks

EGR will do this. It is dumped in right behind the TB.

RemoveBeforeFlight

 

[Vince13]

Breather tube from the valve cover to the turbo inlet is removed.

I will check the EGR valve.

Thanks

 

[turbodave231]

Camshaft overlap (the time that both the intake and exhaust valve are open at the same time) will cause exhaust gases to enter the intake manifold.

I see this on my Stage 2 engine and I know my turbo is in good shape and I have no EGR .

 

[jimmymack87gn]

Carbon coking. Can occur on any MPFI engine. caused by unburned fuel vapors coming back up through the intake manifold via any open intake valves after the engine is shut off. Just clean occasionally.