jbird0007

Was cleaning out my engine bay this past weekend. I took the intake off (FIPK) and saw that there's this black soot-like residue (oil?) all around the butterfly valve. Any idea where this is from? Is it bad?

More info: Car is a MY'00, 40k miles, oil changed every 4k religiously, only mods are FIPK, headers, catback & 70mm HFC. Never had any other engine work done but runs perfect.

zeroptzero

That is very normal, it is just oil vapours from the pcv system and valvecover vent. Airflow form the pcv valved and valvecover vent will introduce oil vapours to that part. I try to clean up the TB plate whenever I have the intake arm apart, but at the end of the day it probably doesn't mean anything in terms of airflow and performance, it just looks dirty.

jbird0007

awesome, thanks!

vtec9

What Jfusion said. Just clean it out, and clean the FIPK tube too.. try to make it all the way back to the inlet from the 1/2" vent hose between the FIPK and valve cover.

Timbagoo

Thanks! I was wondering the same thing with my recently acquired '01 AP1 as I don't remember this when I had the '08 AP2.

Moddiction

Yup very normal. If you want to prevent that you need to get a vented catch can and then cap off the nipples on the intake manifold from the valve cover. No oil would be able to get into the intake manifold then.
I had a puddle of oil in mine when I checked from being boosted and still having the lines coming from the valve cover to it.

vtec9

AP2s still vent the valve cover directly into the pcv/intake system, but they don't seem to suck out oil like AP1s. This is a main contributor to oil loss in AP1s, and why the intake/throttle body get dirty.

vtec9

Krank vents also help prevent it, but are not perfect. The downside is pressurizing the crankcase, which isn't the best for your seals. I ran KVs on both valve cover vents for years and over 100k miles, but just removed the KV from the front 1/2" vent because I developed a real nasty sounding air leak.

Moddiction

I ran the supra pcv for a bit. I just ditched it and vented the valve cover and capped the intake manifold. Guarantee no oil on intake that way.