If it's always CEL with cylinder 3 misfire, it could be the injector. Move the injector down one cylinder to see if the CEL follows #3 to cylinder 2, giving a random misfire in cylinder 2. If so, bad injector. Could also be wiring to injector from PCM if it stays at #3.
Just got my first CEL yesterday leaving work yesterday. It popped on under normal acceleration leaving the first stop light, and I didn't notice anything strange. It was driving smooth so I kept driving home babying the hell out it. It only has 10,700 miles.
Dealer said it was a P0300. Ignition and fuel pressure were within spec, and it ended up being the crank sensor. They found a lost wave form from the sensor at rpm over 2500. The gap between the sensor and the target wheel was "out" (too big i'm assuming). They put the gap back in spec, and everything's fine.
It's still early since it just got fixed this morning, but hopefully that's all it was. Thought I'd throw that out there since I didn't see that anyone else getting P0300's had checked this. Good luck.
