Code P0301 is exactly what it says. The # 1 cylinder has a misfire. This can be caused by a few different things.
The P0301 code means that the cylinder 1 is misfiring or is randomly misfiring. Start by checking for intake leaks an if no leaks are found the next step is to replace the spark plugs on cylinder 1. If the problem persist more tests needs to be done to diagnose problem.
Next thing is to remove the plug and examine it, if the electrode is not rounded then place it in the wire, let it rest against the block and crank it over.. see if it sparking. This rules out the coil pack , plug and wire unless they are damaged and arching. Examine closely. If in doubt, replace them. Remember the problem is only in cylinder # 1. See if the fuel injector is firing. Check compression in relationship to # 2 cylinder. More than likely you just need a good healthy tune up. Go ahead, its probably been a while anyway. After that, treat it to a nice fresh tank of High Octane.
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring.