Black Soot on Intake Manifold

[polaris]

Hello,

I notice black soot on intake manifold toward firewall of engine bay.
Any idea what might be causing this?

Front View
https://picasaweb.google.com/lh/photo/9 ... directlink

Right Side View
https://picasaweb.google.com/lh/photo/3 ... directlink

Thanks in advance

[Towncivilian]

Clean it off and see if it reappears. Also, ensure all vacuum hoses in the vicinity are tightly connected and not leaking. The weather stripping directly behind the soot looks pretty dirty in comparison to the rest, is it still sealing okay?

You have a black 2001.5 LE, 4WD auto w/ LSD, leather, heated seats, sunroof, side airbags, gray interior, and the rare VCR thing in the trunk, right? Loaded!

[polaris]

Thanks,
I don't know if sealing is ok or not. Sometimes I hear whistle at WOT (3000+RPM), but I thought this was something to do with Air Filter Box. After Inserting K&N Drop Filter, the whistle got louder.

Yes, It's fully loaded Pathfinder.
BTW, how did you find out the details of my car? Wow..

[Towncivilian]

The VIN is printed on the firewall, and I looked it up in the Nissan FAST system.

Also check that the intake plumbing is tight and has no leaks where air can enter. Out of curiosity, why are you running a K&N filter? I personally think that an air filter whose media must be oiled rather frequently proves that the media alone is incapable of doing an acceptable job at filtering compared to a traditional paper type air filter. I'm typing this from my phone, I'll write more about air filters later perhaps.

[polaris]

Thank, I will check the Intake plumbing area tomorrow.
For air filter, I am getting 1-2+ mpg gain over K&N Filter.
K&N 15-16 Combined City/Highway vs Paper-Filter 13-14 MPG