Noobie here, first time posting. Did a lot of looking around on the forum but was wondering if my circumstances were different. I recently bought a 2003 g35 at 157k, basically stock but the previous owner absolutely didn’t care about it since there were NO service histories, or receipts whatsoever. (Background info: Has 3 other codes currently, p1564, which I’m not too sure about, p0507 which I believe has something to do with cleaning the throttle body, and P0327 which I’m sure is just the knock sensor i have to replace.) The other day I was planning on changing my valve cover gasket since I figured better safe than sorry. I had only semi-removed the upper plenum until I realized it was going to rain soon so i quickly bolted the upper plenum back on. Out of curiosity, I erased the 3 codes I had and took it around the neighborhood to see which ones would come back on. Ended up running out of time since school was out and I had to get back before the school busses started rolling in. I checked for any new codes and got the P0300 which wasn’t previously there. I know that this is a random/multiple misfire (I had noticed the car sputtering down the drive) which hadn’t been occurring prior to removing the upper plenum. Was wondering if I was a bit too rough with the upper plenum and somehow damaged the spark plugs/coil packs or something to cause the misfires?

 

The gasket is not intended to be reused. You may have created a vacumn leak by doing so.

 

Would that be a cause for a misfire/would finishing the gasket swap be a solution?

 

Make sure you didn't pinch the oil fill neck between the plenums. That's the typical mistake.

 

Would the oil filler neck have to be replaced if its been pinched?