Pinking issue on '03 JDM 350Z

[cb350]

Hi all,

 

This is a bit of a resurrection of an old issue I reported last year, and I've never got to the bottom of it.

 

Basically, around March 2019, I took my car for an MOT, left it there at the garage overnight, and when I got it back it was running bad and pinking.

 

I haven't been able to get to the bottom of what's causing this pinking. Basic order of events is:

 

- End of 2018, I changed the spark plugs and coil packs - all fine

- March 2019, took the car for an MOT

- Afterwards, when it was running rough, I found that two of the plugs to the coil packs had come loose. Reconnected them, rough running went away but the pinking remained

- I've now also changed the injectors, the knock sensor and the ECT sensor - still it keeps pinking

 

Have tried the usual things like attempting to reset the ECU, also I've always run the car on super unleaded. I've had just over 10 years, and never had any problems with pinking before this. There are no fault codes reported by the ECU.

 

The pinking generally occurs between 2500 - 3250 RPM and if I drive *extremely* carefully in that range (coupled with changing gear at different times), I can basically keep it under control. My fuel economy has dropped off quite badly as well, but I don't know if that's a feature of my new 'engine protect' mode of driving!

 

Could low compression cause pinking? Not sure what I should test/change next. MAF?

 

Any help greatly appreciated.

 

Cheers,

 

Chris.

[Bry]

Head gasket failure between cylinders causing compression loss ? I'd do a compression test + leak down test

[cb350]

3 hours ago, Bry said:

Head gasket failure between cylinders causing compression loss ? I'd do a compression test + leak down test

Thanks Bry, is that likely to lead to pinking, with no other symptoms? I keep wondering about low compression, but in all other respects, the car seems to be driving fine. It uses a lot of oil, but then it always has (I've had the car 10+ years).

[Bry]

Yup, no other symptoms. 

[Mark@Abbey m/s]

oil usage could be causing issues as it lowers the octane rating of the fuel. 

 

Few other ideas

 

lean fuelling- air flow meter failings fuel pump dropping flow

air leak (would normally throw a DTC thou

 

[cb350]

Thanks Mark and Bry, this gives me a few other things to look into.

 

I keep thinking about the fact that it was fine before I took it for an MOT, and pinking when I got it back. Usually I drive the car to the MOT station at the time of the test, and it goes straight on the ramp. Due to work commitments, last year I left the car at the garage overnight for them to test.

 

I've always felt my oil usage was high (about a litre every 1000 miles), so I'm thinking, maybe they revved the hell out of the engine to get it up to temperature for the emissions test... if something was just on the cusp of wearing out, I wonder if that could've pushed it over the edge and started the pinking?

 

Something else I just remembered - when I got it apart to change the injectors, one of the inlet ports was a bit oily. I wouldn't say it was really bad, but you could see the difference between the five shiny clean inlet ports, and the one with oil in it.

 

I think compression test is probably a good idea next, I've booked it in at a local garage. Don't want to go down the rabbit hole of replacing even more sensors/components/etc if there's something more serious going on.

Edited January 10, 2020 by cb350

[cb350]

Just coming back to update with the latest - the long-and-short of it is, it seems to have been the PCV valve at fault! If anyone else has pinking with high oil consumption, please just replace your PCV valve *first*, as it's super easy to swap out and not very expensive. Everything else you can do is going to be harder to get to.

 

Longer story:

 

I took the car in to a local garage for a compression test, ended up going through the whole story of why I wanted a compression test, and the guy at the garage eventually decided (after I'd left the car there), that there was 'no point' doing a compression test - he said I was obviously burning oil, and this would make my compression read high (??), but that he had some magic fluid stuff we could try to get the oil burning under control. I just wanted a proper diagnosis, so this didn't really appeal to me.

 

I took the car home, not too happy, but this conversation with the mechanic did get me thinking about the oil burning situation. Oil burning with the fuel is going to bring the octane rating down, so I guess if there's enough oil burning, it's going to get to a point where it starts to pink.

 

So I started looking for excessive oil burning causes, and this led to the PCV valve.

 

I replaced it at the weekend, and the pinking has *almost* stopped completely.

 

I say *almost*, because if I accelerate fully WOT, there is a minor amount of pinking at 3000rpm in pretty much every gear. I'm hoping that I'm just burning off a bit more oil before things settle down, but I'm also wondering if the PCV valve is only one problem, and there is an impending bigger problem around the corner, possibly caused by me being unable to stop this pinking from happening for the past 10 months. I've been driving it incredibly carefully to avoid pinking, but some damage must have been done.

 

For now I think I'm just going to drive it for a couple of months and monitor my oil and fuel usage closely to see how it all pans out. Fuel economy has been pretty bad for the past 2 - 3 months, so I'm hoping this might recover a bit, and obviously I'd like to see the oil consumption improve.