I noted on my 2000 Kia Sephia, with 40,000 miles, that after starting it up,
it began chugging (missing) and check engine light came on.  I took it to
the dealer and they wanted $130 to change plugs and spark plug wires.  I
felt this was unacceptable so looked into the problem myself.  Spent $20 for
four NGK platinum plugs and $20 for aftermarket (2 plug wire set).  Runs
fine now except never was happy with the fuel economy.
Kia recommends changing plugs and wires at 30,000miles, which I though was
kind of premature, but after looking at the plug wire tubes, I understand
why.  Found a pin hole burnt through the tube shorting the spark to ground.
Good thing it wasn't one of the two coil/plug combination part.  That could
have cost me.
I mention this because owners with similar problems might want to check the
sparkplug tubes first.

Tom from Pensacola, Florida