Check these three

• Bad Fuel Injector– I you have a fuel injector that has gone bad, it won’t be able to properly atomize the fuel and you’ll get the P0301. Here’s a good video on how to diagnose an injector, but it can be a little tricky. This is definitely not the place to start.
• Vacuum leak– If your Camry has a vacuum leak, it can be very difficult for it to get the right air/fuel mixture. This will cause the cylinders to misfire and it’ll throw the P0301 if the leak is around that specific cylinder on the intake manifold. It’s easy (and kind of fun) to chase one down. Popular Mechanics: How to find a vacuum leak.
• Cam or Crank Sensors– This one is very unlikely, but it does happen. If the ECU is not getting the right signal from these sensors, the vehicles timing is not going to sync up and it’ll misfire.