Originally Posted by ScarabEpic22
Welcome man! Another member, and with a good name to boot!
P0300 is a random misfire correct? Have you tried swapping coil packs around? New spark plugs?
That's correct. Here's the story from another thread:
Started with mild miss - showed code P0304 (cylinder 4 misfire).
I replaced the plug in number 4 cylinder, then swapped the coil pack between 2 and 4. I detected no moisture problem nor residue in the number 4 spark plug cavity. I then got P0300 (multiple random misfires).
I swapped coil packs back to original positions, still code P0300.
Since I'd bought the plugs, I changed them all out. I could detect no carbon tracking on any of the coil boots. The only thing I did notice was that the coil packs seemed to have a bit more "spring" when I removed them. That is, they rose a bit when I loosed the bolt - much more than when I replaced them. The plugs are the same size, though they are NGK platinums rather than AC Delco. I was careful to ensure that the boots were landing on the plugs. Still very noticeable misfiring both at idle and under load and reading code P0300.
I pulled the throttle body and cleaned it with TB cleaner. I disconnected the battery overnight. Still getting a noticeable miss, but not as bad as before. Took it for a drive and it seemed to perform much better when under load, but still has a noticeable misfire at idle. Still getting P0300 code.
Pulled the MAF sensor and cleaned it. No change.
It seems to run fine at start up, but begins to miss after 30 seconds or so.
Royal PITA. I'm going down to NAPA today to pick up a spark tester. I'm still thinking it's a bad coil pack but I'm not going to buy one until I know for sure. I also don't want to pull the fuel rail until I've tried everything else. This isn't the best weather for working on the car outside...