Ok I had this P0300, random engine misfire, code. I suspected spark plug or coil. So after taking all the plugs (Bosh platinum 4 in a few years now) out and doing a visual inspection and seeing them all in good condition (dry and pretty clean, no build-up) I went on to check my coils. So to do this take your sway bar off for access to the rear coils, start engine and remove and replace each coil wire connector (see video) and listen for change in the way the engine is running. All the good coils will cause the engine drop and lose power when removed, the bad ones won't affect the engine when removed. I only had to remove the front three coils because the middle one was the bad one. I bought a $50 Duralast coild from Autozone and replaced it and wala! I'm back in business I wore a leather glove just for precaution just in case there may be a shock hazard.....

Pic of new Duralast coil in the middle......
http://www.flickr.com/photos/ekxtreem/8799700535/

 

Congrats. Good job fixing it on your own.

 

Don't jeopardize the reliability of you ignition system by using non-OEM Denso or NGK plugs and aftermarket coils.

 

i am not worried about the plugs, i have seen too many posts from people using cheap plugs, they only change them more frequently, the bosch plugs i got are quality plugs and they have been working great for about 3 years now and still going good. i was prepared to spend more on the coil but duralast is all autozone had, my other options were to order online and wait or go to the dealer and pay more than $100 (ridiculous)for the oem and i definitely wasn't doing that. the coil in my car is made by hitachi, i suspect that is the original, i don't think the previous owner ever changed them. i already priced them on amazon and they sell for the same $50 price range as the duralast, i am gonna order 2 or 3 of those and keep them around in case other coils crap out soon and i will get some time out of the duralast then swap it out

 

^Yeah, that sounds good. +1 for diagnosing your problem and fixing it yourself!

 

Thanks bro