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