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Discussion Starter #1
As part of my engine part replacement project, I decided to address the black stuff that has accumulated in the upper intake plenum of my VG33E. At first, I was thinking that it was caused by a faulty PCV, but the valve appears to be functioning properly. Intake ports 4, 5, and 6 were not nearly as bad as 1, 2, and 3, and the source of carbon appears to be the EGR. I posted about this a while back, but wanted to give the thread a bump.

The buildup was the consistency of baked tree sap, and carb/choke cleaner barely put a dent in it. With the recommendation of a local parts store guy that I trust, I used oven cleaner, and it worked beautifully. Intake is nearly spotless now. The question is . . . is there something wrong with the EGR that is causing this buildup? The plenum was a PITA to remove, so I'd rather correct the underlying issue while I have everything apart.
 

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It is probably just from years of driving. Mine was the same way all i did was wash mine out. But it would be ideal for you to go get some throttle body cleaner and spray the shit out of the throttle body and scrub.
 

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Already took care of the throttle body months ago, and it is still spotless. The plenum was a much bigger problem because it is much more difficult to remove. I also was able to clean out most of the gunk in the lower intake manifold using rags saturated with carb/choke cleaner. Next step is to get the last 5% of crud after final assembly, using some SeaFoam intake cleaner.

The PO did not maintain this car very well (if at all), so it would not surprise me if the buildup in the intake is due to carbon-saturated motor oil, burning in the cylinder and being belched out the exhaust (including out the EGR). Can anyone think of another reason for this buildup before I piece everything back together?
 

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Yeah i when i said throttle body i meant the whole plenum. Mine was exactly the same way. I mean unless your feeding oil through the air filter i think its normal wear and tear.
 

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Install a oil catch can

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