Okay, 1998 ex v6 is has a nice little black tail pipe smoke comming out when idle and warm. Heads were replaced so now getting black smoke at idle. Comming more from a GM and Chrysler background I would check to see if the fuel pressure regulator was to high, stuck or punctured diaphram. I would check to see if a sensor would be outputting to high a output. Possible very high vacume leaks would cause this?

What sensors or damaged sensors would cause a high rich running condition on a accord ex v6?

Contamination on the Aiflow sensor wire? Other ideas?

 

Any codes present?
Obviously out of range a/f, so why isn't one of the o2 sensors screaming it's head off and a converter glowing?
I'd start by interrogating the PCM and give the o2 sensors an eyeball as well.

P