P0300

Changing random parts is the most expensive and least effective way to diagnose a problem. It would cost less to take the car to a mechanic.

Code 300 is for a random cylinder misfire. All of the cylinders are involved, but you know every ignition coil and every injector did not fail at the same time. Look at the other things each cylinder has in common. Most notably that is fuel pressure, fuel quality, and air/fuel mixture. A scanner will let you view live data to see how the oxygen sensors are switching between "rich" and "lean".

A vacuum leak is another good suspect. Chrysler is the only manufacturer that never needed a mass air flow sensor to make their engines run right, so problems associated with those are not an issue, but you can still get a lean misfire, and a vacuum leak can affect all of the cylinders.