Ok, I have an '03 350Z, and it has 113K mi. on it so the valve cover gaskets started leaking oil so I decided to change it out. My brother and I replaced it along with new NGK Laser Platinum spark plugs and Oil + Filter Change. Re-installed everything (Torqued to spec, jic). Did Ecu & Throttle relearn. But engine was smoking. Turned off unplugged battery overnight.
Then had my cousin ( a Honda Tech LOL, and waiting on my other cousin to be free who is a NISSAN tech) come over with his SNAP ON MODIS Ultra to test out the engine. Came to the conclusion that 4th & 6th cylinders are not firing up. He narrowed it down to either the harness or fuel. Clueless atm. Any suggestions / solutions / help from anyone will be greatly appreciated.

 

you plugged the coil pack lead for 4 into 6 and vice versa

 

Yes Sir. Any more suggestions?

 

I had pretty much the same issue on my G35 sedan. The issue in my case was my ECU. Try borrowing an ECU from a friend and start from there.

 

Hi Sir,

Your suggestion was correct. I asked my cousin and he told me he did not swap out 4 and 6 coils. My brother and I did what you suggested and it worked. It's running smoothly now. Thank you for your help man. Appreciate it a lot.