Hey everyone,
I've had the 'mysterious P0300' issue happening with my Z ever since I owned it and finally got it fixed this week. So i've made a little write-up that may help someone with similar issues.
About car: It's a 2005, only has 100k kilometers (60k miles), pulls hard and had no issues whatsoever when driving. It was serviced regularly. So there was no apparent reason for car to act up while idling. The dreaded P0300 would appear after standing in traffic for some time, or just warming up the car.
My investigation steps:
- google the problem, heaps of posts of people struggling to find the cause- misfire was audible so it was not a crank sensor problem
- turning AC on would raise the rpm's and would delay the misfire
- replaced spark plugs, checked for vacuum leaks
- it would appear hot and cold, but higher rpm's of cold start delayed the issue for a bit
- had it inspected in official Nissan service. They returned the car free of charge after saying they cannot find the reason after disassembling entire cold side, testing compression, injectors and coils and catalyzer.
- performed ECU reset, throttle position reset etc...
The revelation:
Frantically googling for possible issues and unwilling to accept defeat, I stumbled upon some random forum post about Dual Mass Flywheel causing misfires. Wow! The car never showed any signs of clutch wear or other driveline issues. And failed DMF at only 100k km?
A though pill to swallow where the issue could still persist, but I ordered new clutch kit with DMF. Got it installed last week. Immediately after starting the car there is a noticeable change in idle. Car rides smoother, and clutch engagement is a lot nicer. 1000 euros later, the issue fixed.
I'm also including the pictures of clutch and DMF. No visible clues of high wear to the point of failure.
Also, I'd line to send a big "F* you" to LUK with their utterly shitty moneymaking product called DMF!
Hopefully this post is useful to the people out there