My 1992 Civic SI (D16Z6) always has so much black carbon built up all over the back bumper and hatch. I've done a tune up (wires,plugs,cap'n rotor, O2 sensor) and i've check the computer for any codes and i never get anything but the car still has carbon all over it. The car did come with a chipped computer but i swapped that out and put a stock brain box back in. Maybe the chipped comp messed something up i dunno but the car doesnt smoke it runs great, motor is mint doesnt burn oil so i'm stumped to what the problem could be. Soo, If i can get some help with this that would be awesome.

 

what are your spark plugs gapped at?

 

They are gapped at .060"

 

The original owner probably had it boosted before you. Was the carbon buildup already there or after you owned it?

 

The carbon was there when i bought it. I thought it was gonna be a simple fix but i guess i was wrong.

 

Hmmmm Check and make sure your cat isn't hollowed out.

 

What kind of exhaust are you running and also does the carbon still buildup or is it the same amount as when you bought it?

 

Same **** is happening to my JDM B16