92 accord with 99 accord 1.8 Liter Engine with proper swap and wiring done.
Few days back i started to observe the exhaust tip. It seems that there is slight black debris. It forms after couple of runs. Surely car is not running too rich but slight rich.

Cap and Rotor and Spark Plug Wires are almost new.

I feel i that there is sometimes minor misfires that i cant hear but can feel in car vibration.

Someone said that I should get its injectors cleaned and then tested for flow pattern.

Can it be the cause?

 

All cars will have some soot on the exhaust. Hondas of the 90's will have a bit as they are of a speed density system.
How bad is it? Does your rear bumper also become covered? If you do a lot of hard acceleration/high load, there will be more soot on the tip than a car that is driven subtly.

Don't you have a scanner? Watch the O2 sensor switching. If it it getting stuck in LEAN or RICH mode then you will know there may be an issue.
Also if your car does not have a catalyst this will also contribute to soot/coke buildup.

 

1. No Catalytic Converter Installed
2. No Soot on Bumper. Ill Post picture tomorrow
3. I can get it scanned. Someone said try ELM237 as my car has ODB2b motor with K Line interface.