So here is the story on my car....

I have a 1992 Honda Civic H/B DX and I am the original owner. I had him turbo'd, which lasted a total of 330 miles until I blew the hell out of the stock motor (yes, I know, I should have done internals...) Anyway, I went back to a completely stock system underneath the hood. I purchased a stock motor from Japan. It is the D15B SOHC VTEC. I do not have a header on it; I have the stock exhaust manifold. The motor I purchased had approx. 30K when I bought it, and I've put approx. 10K miles on it. I ride my baby gently and do not race it at all...afterall, she is stock now. I just switched to fully synthetic oil a few weeks ago. I make sure I keep her changed ever 3K. Now to my problem...

I've noticed a carbon build up on my rear bumper. I put my finger on the inside of my exhaust tip, and I've noticed a dry dark black carbon build up on my finger. Now, my exhaust is 2.5" from the high flo cat, all the way back. I am going to a stock type system. My engine does not burn/drip a drop of oil, and she runs perfectly, w/ the exception of this carbon build up. I'm concerned about it, because I just gave her a bath a few days ago, and I'm noticing this carbon build up. When I had my baby turbo'd, I was gong through a quart of oil a day and had it plastered on my rear bumper. For giggles, I started my baby up and I put a white paper cloth in front of the exhaust tip. I literally had a few specs of stuff on it, but nothing major...I do mean literally a few (less than three little specs of carbon.) Furthermore, I do not notice any blue exhaust coming from my tail pipe. What in the HELL can be the problem? I'm going to take her into the speed shop today when I get off work. I'm very concerened about her, because I'm not made of money (who is???), and I can keep on swapping out motors every 12 months. I do not have the heart to get rid of her either...afterall, she is my baby.

 

One more thing, I did the motor swap this past July, and this is the first time I've really noticed it. Could it be residual? Could my cat be goofed up? Will my new exhaust system take care of the problem? HELP!!!!!!!!!!!LOL

 

ive had the same problem..... previous motor was blown when i got the car and it was extremly bad when i first started rocken the new motor....
I HOPE it was just residual crap in the exaust! but i have yet to get new pipes and new resonator as well to go with my new muffler...

BUT so far just geting the muffler sticking past the bumper alittle its not building up on the bumper as much... but i can still see the black crap on the inside of the piping. im hoping new pipes and resonator will solve the black crap from building up BUT no idea... but till then geting my new muffler sticking past the bumper has helped alot!

 

i'm in the same boat...obviously. I will let you know what I find out when I get my new exhaust next friday....it's really frustrating to see that's for sure. I appreciate your response.

 

how far is your exaust tip sticking out from the bumper?
my old fart can muffler was actualy siting just behind the bumper so it covered the bumper VERY EASILY...

but if its a stock exaust you could always bolt a exaust tip on it to lengthen the exaust pipe past the bumper a bit...
i would recomend 1-2inches past the bottom bumper lip...

 

about 6"....if that....it's not a lot of carbon, but enough to **** me off.

 

Yup, you've probably got crap in your exhaust. Swap those parts for new ones and check it then. If you've still got carbon, it sounds like incomplete combustion. You'd be running too rich or your ignition isn't working at it's best.

If you aren't ready to swap exhausts right now, at least check your plugs for carbon buildup, to see if the problem could be BEFORE the exhaust.