What could be the cause of black carbon deposits on the spark plugs of my peugeot 405?

It has a carburation fuel system and someone had advised that the air %26amp; fuel ratio is not propotional and i need to know how i could solve thisWhat could be the cause of black carbon deposits on the spark plugs of my peugeot 405?Who ever told you that it was the air/fuel ratio is right. Too much fuel... If you don't know how to adjust a carburetor then don't mess with it. Find a tech that understands carburetors. Some younger techs have never adjusted a carburetor and won't know if they got it right. If the carb cannot be adjusted you might be looking at a rebuild. Good luck..What could be the cause of black carbon deposits on the spark plugs of my peugeot 405?02 sensor can do that, also if the carb. isnt adjusted right can do it too, especially if the choke isnt working right.