I just want to throw this out there for other that may get the p300 multi cylinder misfire.

Mine ended up being a failing ignition coil pack. When I say failing, from a cold startup, I noticed the engine would run smooth for about 15-20 seconds then sputter. After 15-20 seconds the coil electronics start heating up and fail.

To get to my solution, I changed plugs which were needed anyway and tested each coil pack for resistance as suggested in another post. All the coil packs test ok for resistance. I then followed the method of disconnecting each coil pack to observe engine drop off. When I found the faulty pack I marked it and moved it to a different cylinder. In my case #5 was bad and I moved it to #1 and tested the engine drop again to confirm it was that coil pack I moved to #1. I replaced the coil pack and runs great again. Coil pack was ordered from rockauto ~$37 for a OEM Hitachi coil pack.

Hope this helps if you have the same symptoms. P300 can be a pain in the a$$.


2004z 130k miles and a modified AEM intake, got it used.

 

Great! thanks for that info! I'm having the same error code but I think my problem is different.
My car runs fine until I start accelerating I lose power and all the spark plugs smell like gas.

Thank you nevertheless!