So I recently started having a handful of problems with my base 2011 g37 160k. It all started when I was going 140mph way up in the rpms when my motor started misfiring. Took a look at everything and the codes p0300 random misfire & evap small leak and I came to the conclusion that I had broke the sparkplug gasket (driver's) so I replaced that and the valve cover gasket on my driver's side, along with all 6 new NGK Plugs. Went to start her up and still getting a misfire except now it's giving me codes for random and cylinder 4. On the Driver side the first cylinder and the last cylinder were the only ones where I found oil in the sparkplugs so those were the ones I thought to first replace the coil packs at. I got 2 cheap but not cheap import directs coil packs from oriellys and I put it in firing cylinder 4 and boom she drives fine for a solid 24hrs then starts to misfire again this time codes claim from cylinder 3 and random. I put a used plug from one of the cylinders that had oil with the spark plugs in it, in place of the newly misfiring cylinder 3 for ****s and giggles and still no avail. If I get 4 more import direct coil packs do y'all think I'll resolve my issue? My mechanic said it could also be my fuel injectors?

Replacing Valve Cover Gasket

NEW PLUGS, CORRECT ONES??

 

strange post, but first thing misfire is detected you should:
1.Check spark plug.
2. Compression test.
3. Leak down test.
4. Check if rail holding fuel pressure.
5. Try switching coils.
6. Since it happened on WOT check if timing in marks line up.

 

So since then I have received these codes
P0113 Intake Air Temperature Sensor / Circuit Bank 1
P0102 Mass or Volume Air Flow "A" Circuit Low Input
& A few more ( lost my list of codes, will add the rest asap)
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if code calls for MAF sensor, why not try to switch sensor with another bank?

 

Just replaced with MAFs and nothing changed.. I remember I had a code for my catalytic converter and the computer jockey at O'Reilly's recommended some cat cleaner but I can't recall the code. Also as of recently when I had determined which coil pack was failing. I stopped getting codes for specific cylinders misfiring now it's only random misfire as far as misfire codes go. All the other MAFs codes remain. With that being said if led me to believe that an air/ fuel or catalytic converter issue is the cause for the misfire

 

Being that you had oil in your plugs already means that the remainder coils probably have oil in them.

A good practice when I do service is to disassemble the coil tube and wash everything in degreaser.
I later take the coil tube and paint it (tubes are porous and spark can jump when theyre on their way out, paint helps seal this surface)

As for plugs you need Denso plugs (expensive ones) NGKs will work but finding a misfire issue with NGK plugs can have you replacing everything.

Start with cleaning the old coils first, switch some of the coils and plugs around as well and keep trying.