Black carbon soot

CHETAN

MEMBER
2001 HONDA CITY
160,000 MILES

Throttle body starts accumulating black soot in run of 50 to 100kms after I clean throttle body. I have also cleaned PCV valve which also accumulates soot along throttle body.
My car's ignition timing is right, I would like to know if tappet settings valve clearance as.007 inch for intake and.009 inch for exhaust is correct. Is it ok to keep exhaust clearance to.010 instead of.009? Any other tips which can help me reduce black carbon soot. Also compression test of all cylinders show 1st-190, 2nd-200, 3rd-200, 4th-200.

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

On gasoline engines the only way you are going to continue to get soot in the throttle body is you have excessive blow by, and you are pushing oil through the PCV into the air intake.

This means we need to remove the oil cap when the engine is running and see if you feel air pushing out which would indicate the issue is the oil is coming up through the intake system.

One sign of this is smoke from the oil fill cap or exhaust so let's check this and go from there.

Here are a couple of guides that will help:

https://www.2carpros.com/articles/engine-black-smoke

https://www.2carpros.com/articles/blue-smoke-from-engines-exhaust

Please run through this info and let me know what you find, and we can figure something else out if this is not the issue.

Thanks