1.4 75hp runs on 3 zyls.

Hello, a friend of mine has a 96 Escort with 1.4L petrol. It runs sporadically only on 3 cylinders, especially when it is warm. A spark plug is black or badly worn, all the others are ok. Can one somehow read a fault memory with the Escort? I drive a 2001 VW Lupo and own the corresponding ODB interface, the question is only whether this is at all standardized, or only works with VW engines. Or else there are any typical errors with the EDB I had the same problem with the Lupo, because it was the ignition cables. Is that also known with the Escort? Is it a bit stupid, because you can’t see the effects directly without OBD, for example, if you exchange 2 cables with each other. Do you have an idea?