My Hyundai Accent is misfiring, but the coil packs are fine. What's wrong with it?

You installed new spark plug wires and it ran fine. So recheck the new wire connections to the spark plugs. Check your owner's manual to see when the spark plugs need replacing. If your friend punches the accelerator at night with the car in park, parking brake on and hood open, you will see sparks jump off the new wires if you've still got a problem with the wire connections. Make sure you stand along the driver's side fender in case the car lurches forward. The engine compartment has to be in complete darkness to see the sparks.