If the fuel filter on a 1999 Kia Sephia is plugged would it cause the check engine light to come on and the car to run badly?

Answer 1

First of all is your car acting like it doesnt have much power and it wants to die. I had the same problem and it was my catalytic converter the 2nd one there is two not the one connected to the motor. It was clogged and check engine light stayed on it was running terrible so check into that. I changed everything else i thought it could be and it was still doing this so i took it to diagnostics scan and that was it.YES

Yes; although the computer won't report a clogged filter directly, the OBD code will usually resolve to a "random cylinder misfire" or something similar.