Hi, first time poster. I just bought a 92 civic cx with 129k miles, good condition, runs good. As far As I know the only after market mod is the fart cannon. I am pretty sure that the engine was tuned by the previous owner.

I have been driving it for a week or so, the mileage seems on par with specs at 35-40 mpg. I noticed the other day that there wasa bunch of black dust on the tail gate. When the engine idles, the exhaust is fine and the engine sounds normal. no smoke or gas comes out of the exhaust, but when I rev the engine, black smoke and gas spew out of it.

With my limited knowledge of engines, I deduce that there is incomplete combustion and the fuel injection need to be adjusted

I am going to put some fuel injector cleaner in next time i fill my tank and then maybe some fuel system cleaner, but not sure what else I should do about this.

If any one could help it sould be greatly appreciated.