Multiple Cylinder Misfire P0300

Genosphere

So my Z threw the code a couple of weeks ago and i finally got around to checking into things. To start from the beginning I went to start up and take the car for a spin on a pretty cold day, 2*C-ish, during idle before i pulled out of the garage my foot slipped of the clutch and i stalled it out when i reached to close the door. So after maybe 5 to 10 min of driving i noticed it would not go above 2500rpm, it bopped it back down every time. Plugged my OBD and pulled the code, P0300. Got it back home disconnected the battery an came back the next day fingers crossed; nope. So after cleaning and plugging it in the Lim mode was not set at 3500, then it went to 2500 again after i checked on it another day, basically 2500 most of the time. Ill upload some pics for visual aid.





The spark plugs all look about the same, I cleaned the MAFS, disconnected each coil during run with each causing a noticeable unbalance, disconnected the battery for a while to try and clear anything. The plenum as you can see looks to have oil/gas or some residue all around the O ring, this looks odd to me. I think there maybe a vacuum leak; possibly a bad O2 sensor caused by a vacuum leak?

I have been going going off a check list off a 350Z forum:

""MUST READ IF YOU ARE HAVING THIS PROBLEM.

So my car had some issues that I starter to take care of a week ago since im selling it.

steering angle sensor - all it needed was a reset.
cam sensor - changed bank2: driver side

now for the random misfire/sputter.. this is a good check list to follow:

I first got the imfamous P0300 code.. which could be so many things!!

1. MAF. dirty or bad- buy the crc MAF cleaner spray from autozone and clean or replace or swap wiht a buddy.

2. CHECK / OR CHANGE SPARK PLUGS.

3. INJECTOR STICKING OPEN? - check spark plugs to see if you find "the black one" if you see a spark plug that absolutely looks different and completely black then the corresponding injectors needs to be replaced.

4. O2 sensors- change if you have any o2 sen codes

5. Clogged cats??-your cats might be cloggedd.. easy way to fix: take out the 2 o2 sensors that plug on to the cats. turn the car on.. if the sputtering/misfire goes away AT IDLE- then your cats are clogged. if you still have misfire at idle then your cats are ok.

6. check coil packs!- easy way to narrow down the culprit is to turn the car on, and while the car is one start disconnecting one coil pack at a time.. if the car dies down or idle changes then that coil pack that you just disconnected is OK. if you disconnect a coil pack and there is no change in the way your engine is running than that is THE PROBLEM!!.

7. vacuum leak? - check intake for vacuum leaks, you can also take off the plenum and check for oil or gas on the intake.

8. PCV valve- change it!! its only $10 on ebay. located on the pass side valve cover.

9. CHECK ALL INJECTOR/COIL PACK CONNECTORS AND HARNESS.

10. MAKE SURE TO CONNECT THE RIGHT CONNECTOR FOR THE COIL PACKS IF YOU DISCONNECT THEM.. CYLINDER 4 AND 6 GET MIXED UP.. CYLINDER 4 CONNECTOR HAS ONE SOLID GRAY WIRE AND CYLINDER 6 HAS ONE GRAY/RED WIRE.

11. bad gas can also lead to misfire.. and so can a clogged fuel filter..


MY PROBLEM ENDED UP BEING A BAD COIL PACK. AFTER I CHANGED ALL 6 INJECTORS AND NEW MAF, I RESET THE ECU (http://www.technosquareinc.com/350reset.htm) AND TOOK IT TO AUTOZONE TO GET THE CODES PULLED AGAIN.. FINALLY GOT P0301 WHICH NARROWED DOWN TO CYLINDER #1.. REPLACED THE COIL AND BAM!! CAR WORKS LIKE A CHARM. HERE'S THE VQ35DE CYLINDER ORDER ALSO.. AND THIS WEBSITE IS HELPFUL IN FINDING OUT WHAT THE CODES MEAN (http://nissanhelp.com/index.php)
THIS WAS A HEADACHE FOR ME AND JUST HOPE I CAN HELP OTHERS.. ALL THIS INFO WAS GATHERED FROM THIS FORUM, FROM DIFFERENT POSTS.""

Any insight or idea on the pics and info I posted would be awesome.
Thanks