My car misses for a brief period after starting it for the first time in the morning. It misses on cylinder 4 (P0304). It clears-up fast and runs perfect the rest of the day. What would cause this?

Thanks.

i would try moving the wire first, check the plug and coil terminal for corrosion. lesser likeliness a injector oring that seals as it warms up.

Cracked spark plug or plug wire that arcs out to ground when wet. As the engine warms up and burns all the moisture off that accumulated overnight the problem goes away. You could probably duplicate the problem by spraying (fine mist) the #4 wire and plug with a spray bottle of water. Do it when it is dark outside and you will probably see blue flashes.