The car in question 2005 Altima 3.5 5spd. 92,000 miles.
I've owned this car for five years now and it gets a p0300 code randomly. I'd say every 10,000 miles or so. There has never been a sign of hesitation or any hiccups.
Saturday I installed new NGK iridium plugs, pcv valve, NWP phenolic 5 pc. spacers and VIAS block off plate .
I'm still getting this code...... after 40 miles of all the new goodies, another p0300.

Any ideas as to what could cause this?

Hey Lance!

For the sake of being thorough, a code P0300 may mean that one or more of the following has happened: Faulty spark plugs or wires Faulty coil (pack), Faulty oxygen sensor(s), Faulty fuel injector(s), Burned exhaust valve, Faulty catalytic converter(s), Stuck/blocked/leaking EGR valve / passages, Faulty camshaft position sensor, Defective computer.

I know that the 05-06 VQs had an issue with the cam/crank position sensor. This could be the cause of the issue. Another possibility is an O2 sensor. My instinct is that it is something electrical since it is something intermittent. Mechanical problems rarely fix themselves.

Someone else may chime in with further guidance. If you can come up with anything else that may help in the troubleshooting process, post back. Hope you get it narrowed down.

Thank you!
I will try the crank/cam sensors next. this has been an on-going code since 30,000 miles. I just recently installed a grounding kit to hopefully help electrical issues.

keep us posted! I would like to see you come to a resolution to your problem and have us document what it was here. We are all about problem solving here.

UPDATE

I'm currently at 115,000 miles and have not got the code since. So I'm guessing the gaskets/spacers took care of the problem.

I've also recently installed a new clutch master cylinder and one piece maxima clutch line and what a huge difference!!!

Also ordered new gr2/sportlines, can't wait to put these on.