Curious...Normal Intake Buildup?

[westphaldp]

I'm finally replacing the faulty knock sensor on my 2004 Silverado 1500 5.3L (code P0332) and noticed some unexpected oily residue in the intake ports of the cyliner heads. As I've never pulled the intake off of an engine, I don't know if it's normal or what is causing it. It has 160k miles on it, but I wouldn't think that much oil would come through the PCV.

 

Is this normal or should I be concerned?

Where is it coming from and what is it?

Should I do anything with it before putting the intake back on?

 

I've already wiped down the gasket seating area with brake cleaner, which revealed the slightest scratches from the intake manfold gasket. I'm not sure why the gasket would score the surface, but it appears that it has. I'm not very concerned about any of this, just curious.

[westphaldp]

I've done some research on this and found that it is common. Much more common than I'd like. It is a result of the PCV setup on these engines. The solution is to install a catch can into the PCV return (head to intake manifold) line. From what I've found, the Rx Speed Works (or RX Performance) seems to make the best. A kit can be had for a few hundred bucks.

[Explorer]

At 160K I would expect "some" of this to be normal. PCV could surely be a cause, as could slightly leaking valve stem seals indicated by slight smoking at startup. The longitudinal scratches appear to be from a previous clean up of gasket material. I've seen this on engines with far less mileage. A good live data scan will probably show up a cylinder misfire. New plugs, while not a cure for the buildup, may help burn of any oil getting into the cylinders.