I was checking my install of my K&N Filtercharger kit on my '99 Expedition. I pushed back the butterfly and inside the t/b is covered in a thick film of black oil. What would cause this? The PCV maybe?

 

and tube.
What the heck is this and where did it come from?? Please help and identify. Thanks in advance. Jim

 

I may have come from your K&N filter. Check the rest of the tube area for the same oily stuff.

 

I have run into the same problem. It caused me to run lean and the check engine light had come on. I brought it in to be serviced and they said the throttle body was gunked up. They sprayed some TB cleaner in it and since up until 1 month ago it was running great. I have not yet opened it back up to see if more has formed. I also run a K&N FIPK (installed after the TB was cleaned out), I do not think that the K&N is contributing to the problem.

 

The black stuff in there is probably from your Exhaust Gas Recirculation Valve (EGR) and is normal. The wife has the truck right now or I'd verify it. I do know that's the case with 5.0 mustangs though. Follow a hose from the EGR and see if it doesn't go in some where on the TB, probably by the idle air control valve which reintroduces exhaust gas back into the induction.
If you ever have idle problems take the IAC valve off and clean it with solvent and it may help.
BTW, I believe ford will replace your PCV for free at around the 60K mile mark.

 

A slight film of black oil is probably normal behind the TB butterfly. This is due to the exhaust gases being fed back up into the intake by the EGR and other emission's component's. If it's very heavy oil really caked in there you may have problems. You can get throttle body cleaner to clean it out just don't use rags. Some throttle bodies are coated with a specai lcoating the resists carbon build up so be sure to get a cleaner that says "coating safe". I know mine is fairly black but not to bad. The dealer can clean it out and they seem to always do a better job than what you can do at home with aftermarket stuff.

 

Most motors get this buildup and its all cleaned out when you go into "service" your vehicle. My '91 had this crap soo thick in the intake tract that it looked like someone had poured a bottle of molasses in it. My '91 was bone stock too.
"Intake gunk happens"
- Nealio