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P0300 misfire while idling finally resolved


stirkac

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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

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Is this the original kit from 2005? Unless you or someone else changed the clutch on a like for like basis, or abused it for it to wear early, I can't see how it's the fault of LUK. We do a lot of their kits at work & never have any comebacks. I had the clutch done in my sisters Golf over xmas, symptoms were it felt like a misfire at idle, lumpy, but it ran fine. It turned out the DMF had gone out of balance. New LUK kit was fitted & it's been spot on.

 

How old is the kit?

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Yes it is factory installed kit. My mechanic confirmed that transmission has never been removed before. I've added a photo of all PNs, you can also see small LUK logo. By the looks, both clutch and transmission had low wear and no discoloration. That's as expected from previous owner usage, him having car since new and being over 50 years old.

For what the price is for DMF (me being no professional) I think the quality is shoddy. "Burned" welds, casting marks everywhere and even a copper balancing weight on one side. For something worth £500, meant to be spinning at 7k RPM?

 

Mine could have been just out of balance too, because I couldn't hear any noises related to DMF failure... 

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Clutch components and Dual Mass Flywheels are wear and tear items.

I think that you have done very well getting 13 years out of these parts.

I think that it is a bit harsh criticising LUK.

Also “Burn” weld marks are to be expected during the manufacture of the LUK DMF.

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I am aware they are wear and tear... 

I am more angry at the fact that this phantom P0300 haunted me for so long and it turned out to be the flywheel of all the things, without any apparent signs of failure. I guess it was just 'bad luck'

 

Anyways, I am happy with how my car runs now, and that's all that matters! 

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50 minutes ago, stirkac said:

 

I am more angry at the fact that this phantom P0300 haunted me for so long and it turned out to be the flywheel of all the things, without any apparent signs of failure. I guess it was just 'bad luck'

 

Then perhaps you should be venting your anger at the garage who took so long to diagnose this for you.

This fault is much more common then you would believe and is quite a straight forward diagnoses for the informed garages.

However, as you say, the main thing is that it is sorted, so go and enjoy your car.

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4 minutes ago, ZMANALEX said:

This fault is much more common then you would believe and is quite a straight forward diagnoses for the informed garages.

I'd like to agree with you on this one, but as pointed out in OP I got it diagnosed at national HQ Nissan service centre. They looked up Nissan's database for 350Z servicing, torn apart half of engine, made all sorts of tests, chatted with Nissan tech in Japan directly...  and gave me the car back after 16 working hours for free (which is a miracle itself).

 

Anyways, I'm going to rest this debate here :) 

 

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