Anyone here familiar with these Honda Accords (1996). I have one with a F20B Twin Cam (blue cover engine) and on idle, black smoke comes out of the muffler, every once in a while in a cycle, like a timed cycled. The idle also sounds different when this happens. Would anyone have an idea what this might be? Second engine change and I have the same problem, also changed the throttle body. The only thing I noticed was the brain was H23A I think. Don't know if that would need to change.