I assume you know the problem is a misfire in #2 cylinder from checking the diagnostics code. Although these codes can be helpful in narrowing down a problem they lack specific details. In the case there are several possible items that could trigger the engine fault code P0302
- Faulty spark plug or wire
- Faulty coil (pack)
- Faulty oxygen sensor(s)
- Faulty fuel injector
- Burned exhaust valve
- Faulty catalytic converter(s)
- Running out of fuel
- Poor compression
- Defective computer
Before you spend any money to resolve this you need to narrow this list down even more. Start by pulling the plug. Do a image web search on "spark plug diagnosis". This will give you pictures of plugs with a variety of problems to compare with yours and give you an indication whether or not the plugs need replacing. Next if possible switch #2 plug wire with another. Make sure you switch both ends (coil end and spark plug end) of the spark plug wire.
These are the no or low cost options. Beyond these you will need to start replacing items like the Ignition Coil and O2 sensor.
If you are still having the problem after checking and/or replacing the items listed above, your next step is a compression test on #2 cylinder.
If you get to this point please repost here with the results with the wires and plugs and I will give you the steps to follow with compression testing.
Hope this helps.