I just noticed it last night when I was getting on it real hard and could see it in the headlights of the car behind me. Is the car running rich and just burning off extra fuel in the cylinder? Should I check the plugs to see any are fouled. I have noticed the idle is a little rough when cold.

 

I think the car may be a bit rich at WOT.

If I noticed that consistently (what you are mentioning), I think I'd head off to a dyno and see what the A/F mix at WOT was.

I do notice the exhaust after running slow around town, then stepping on it with the sun at my back or at night with lights behind me when I stomp on the gas. The second time I stomp, there is no "junk".

IMO, I think our cars run pretty rich at WOT depending on weather, temp, etc.

And -- the car is pretty dirty during open-loop operation (cold in the morning). It's possible that a bit of "junk" collects in the mufflers/exhaust and doesn't get blown-out until you stomp (who knows for sure????)

I like to quick detail the car and notice some black at the back of the car (bumper, etc) after a day or two of driving. Low-pressure, at the rear, helps soot (pollen/dirt) collect there, but I'm pretty sure it’s from my car. (As a note -- when I stay in grandma mode and don't "blow the car out", the back of the car stays "cleaner".


If you plugs were "fouled", you would probably get a misfire if it repeated under the same condition, you would get an engine light. If you needed to look at a plug, you would have to cut the engine at WOT, and without a clutch this is hard to do (get a snapshot of the engine operation at WOT).

See link (this is what I used to do with Webber carbs when not near a dyno. I also had a manual tranny [clutch] and a fast hand for the ignition switch):

http://www.airheads.org/contrib/readingsparkplugs.html

However, there is a problem with an automatic vehicle:

"At the end of the distance, snap the throttle full off and pull in the clutch and shut off the engine..."

 

Nerver saw it while driving, but my silver car gets soot all over the back bumper after a few days of driving.

 

While in the VTECH the car will burn richer to protect it. If it was to lean out you would have pinging. My Integra, RSX, and now CL all have lot's of soot, on the rear, when I run them hard.