Okay, so I have a 2003 350z with basically unknown mileage, the odometer says 67k but apparently it's not the original odmeter, it's twin turbo with the Greddy kit I'm pushing 5 pounds of boost, anyway it started running real bad about a month ago, turned out it was just a bad mass airflow sensor, replaced that took it for a drive and it ran perfect, insane fast, but then it started to over heat, found out there was a hole in the radiator, replaced that still got hot, replaced thermostat and it still got hot, turned out to be the water pump, so we replaced that put it all back together and I had it out driving for a day maybe two and it ran fine, it seemed like maybe it didn't have quite the amount of power as usual but I wasn't sure, then it sarted running weird, it would misfire when I accelerated hard and sometimes idle weird, so I parked it and the next day it was even worse, so basically when I start it up and drive it it's running horrible, you accelerate hard and it just sort of starts to flutter I guess (misfire) and I loose about two pounds of boost. And at an idle it makes a weird kind of knocking noise and the car shakes a little, it sounds like a real hallow pop pop pop, hard to explain. The computer has pulled up a cylinder 4 misfire which went away and a cylinder 5 misfire which stays. I replaced all the spark plugs and it still hasn't changed anything.. Coil packs seemed to be good and I really don't think it's injectors, but I need help any suggestions would be much appreciated

 

The fix is simple. Have your dealer capture the correct code, and then go ahead with the repair/replacement.

 

That's about it^....Gotta pull some codes.

 

Maybe you're about to throw a rod through the block. Done a compression test? Could be coil or injector, Knock sensor/ harness, and more.

 

The knock sensor and sub harness would retard the timing, definitely making the car lose power, but I'm not sure about any of the other symptoms.