Code 0306, etc.

Hi all, I have a 1998 Plymouth Grand Voyager with 3.0L. Recently, the light comes on and off and code is P0306. I checked spark plug for cylinder 6. It looks good. I wonder what causes it.

Also, the 4 lights for the rear window wiper flash when just start the engine. After a while (10-20 mins), they usually go away. Again, what's the reason?

Thanks a lot in advance.

As for the misfire code you may want to change the plug wires. If you changed the plug then the wire may be the issue. If that doesn't work the next item would be the coil and finally the fuel injector. As for the wiper lights I have no clue!