1993 Honda Civic Black Soot

This is usually due to an improper air to fuel ratio. This could be caused by a number of things. Is your check engine light on? If so, get the codes that it is sending to see if any sensors or other components are bad. If not then you can check to see if your fuel filter is clogged. The mileage of your vehicle is very high so if you don't know when the last time the filter was changed it would be a good idea to go ahead and change it. It can improve gas mileage and possibly fix your problem stated as well.