Money Pit? Help diagnosing 2014 Bentley Flying Spur Issues that 'appeared' after Delivery

[Ziddywerks]

Why do a leakdown or compression test manually? It will be nearly impossible to get accurate results by trying to crank it manually with a wrench or rachet.Disconnect power supply to coils or fuel pump and crank it over with the starter. For leak down you need to put the engine on TDC you will need a bentley manual for that procedure and may need to pull the nose into service position. If the cost is high I would try replacing injector firstl. Changing one injector may resolve other misfires.

 

[Ziddywerks]

I believe the firing order on the W12 is 1 - 12 - 5 - 8 - 3 -10 - 6 - 7 - 2 - 11 - 4 - 9. So it looks like your issue is related to a single cylinder if you ask me.

 

[Uwe]

For some reason I can't post the image but here

Fixed it for you.

-Uwe-

 

[Dr Sheldon]

First question from me is what is that scope connected to on the car ??
What scope have you bought?
How many Channels -
Did you get an AMP Clamp ? -
Am I able to download the software. If so you can ping me the file - that way I can look at it properly - make precise measurements not just look at screen shots !!??
Are you on Whatsapp ? Check your messages !!

as @EuroX has said turning the engine manually would be wrong - it just wont work !! Paralyse Fuel and Spark by pulling fuses

They said it was impossible to get a wrench on the crank.

Too True. As with anything on that gorgeous but 8astard Car.

It wont have to be a money pit now that you have a scope - Long gone are your days of aiming in the dark replacing expensive parts and getting it wrong - Money down the drain
More so it is now possible to offer you accurate help and knowledge that you can use the very same day and gain an automotive advantage from it !!

but they couldn't do it because they were unable to crank the engine manually.

That's a sign of poor knowledge - The engine can be spun from the Starter Relay !! There is ALWAYS a way !!

 

[Ziddywerks]

The engine can be spun from the Starter Relay !! There is ALWAYS a way !!

Agreed jumping starter relay will spin the engine over no problem. I believe if done this way no spark or injector will fire regardless. I could be wrong but I don't think I am in this case.

 

[Dr Sheldon]

Agreed jumping starter relay will spin the engine over no problem. I believe if done this way no spark or injector will fire regardless. I could be wrong but I don't think I am in this case.

Id go with that !! Absolutely correct if ignition is switched off !!

You could power T87 Relay with a wire direct from B+

 

[Uwe]

Thread re-opened for @dn242

-Uwe-

 

[Ziddywerks]

Any updates on this?

 

[dn242]

There was in fact a solution to this issue! I asked @Uwe to reopen the thread to post the final resolution here so anyone who finds this thread in the future can hopefully gain some insight. Sorry for disappearing -- some life issues got in the way and this car sat idle for a while, but it's now a daily driver.

First, a HUGE thank you to @EuroX and @Dr Sheldon for help troubleshooting! Without you, this likely never would have been resolved and I would have sent the car back under dispute. Instead, the car is running perfectly. Also a huge thanks to the VCDS team for providing a tool that can handle everything I've thrown at it related to this Flying Spur.

Solution: The solution to the misfire issue was a failed #4 fuel injector. The injector may have been mechanically clogged, but the problem was electronic and the injector failed bench testing. This caused the fuel trim issues, as well as the misfire codes.

In retrospect, I believe the reason the misfire codes did not always throw for cylinder #4 is because the misfires are detected by the ECU based on crankshaft acceleration. The ECU deduces which cylinder had a misfire based on the current timing of the engine. As @EuroX said in Post #22, the firing order on this W12 is 1 - 12 - 5 - 8 - 3 -10 - 6 - 7 - 2 - 11 - 4 - 9. The misfire codes thrown from cylinders #11 and #9 were likely misfires from cylinder #4, but were sensed as misfires on #11 and #9 because those cylinders fired before/after the real problem. The misfire count for #4 was maxed out, while #11 and #9 were intermittent.

Work done: I replaced all coils and spark plugs (this YouTube video was hugely helpful). I removed all 12 injectors and took them to an injector cleaning shop for service.

I etched all injectors with their cylinder number to isolate problems. As you can see from the attached images, the injectors were all fine and showed some improvement with cleaning, except for #4 which was dead.

Before / After injector cleaning:

Failed #4 Injector:


I ordered a replacement injector for #4 and put everything back together. It worked perfectly . No more misfires and fuel trims normalized after driving.

Final Note: In order to get the car to pass emission testing after resetting the engine, all "readiness" checks had to be completed. This involved a long drive cycle (I'll post the link in the manual if I can find it) with lots steps. After that was complete the car passed emissions and there have been no issues with the engine since.

Thanks again to this forum and to the Ross-Tech team for all your amazing help!

 

[Dr Sheldon]

The misfire codes thrown from cylinders #11 and #9 were likely misfires from cylinder #4, but were sensed as misfires on #11 and #9 because those cylinders fired before/after the real problem. The misfire count for #4 was maxed out, while #11 and #9 were intermittent.

1 - 12 - 5 - 8 - 3 -10 - 6 - 7 - 2 - 11 - 4 - 9

With a faulty injector #4 I can see how that may show as a misfire on #9 and maybe #1 - They fire after #4, If 4 fails to combust then for sure #9 will have to work harder to bring the crankshaft speed up from a lower rpm (caused by 4) There may even be a slight knock on effect on #1 which fires after #9.

None of that explains a misfire on #11 ???

That just makes no logical sense - either that or I have a learning opportunity here !?

 

[RGH0]

With a 12 cylinder engine firing every 60 crank shaft degrees and the power strokes overlapping maybe the ECU detection of acceleration with the two ECUs involved struggles to accurately identify which cylinder is not firing correctly and misallocates it at times.

 

[Eric]

The injector cleaning shop forgot to fudge the "after" static flows to make them more believable What is injector "N"?
Thank you for making the effort to write a feedback post!

 

[Dr Sheldon]

maybe the ECU detection of acceleration with the two ECUs involved struggles to accurately identify which cylinder is not firing correctly and misallocates it at times.

186,000 Mph
Powertrain Can @ 500Kb/s

Clock speed of the Processor ?? IDK

No !! the Ecu's as a pair do not struggle - At least I do not believe so !!

 

[RGH0]

I

186,000 Mph
Powertrain Can @ 500Kb/s

Clock speed of the Processor ?? IDK

No !! the Ecu's as a pair do not struggle - At least I do not believe so !!

agree its probably not a question of ECU processing speed or capability but with the overlapping power strokes its a question separating which overlapping power stroke is the cause of the misfire. Easy on a 4 cylinder much harder on a 12 cylinder. Also the ECU to ECU communication speed may be an issue if that's involved in the relevant cylinders

 

[jyoung8607]

I agree its probably not a question of ECU processing speed or capability but with the overlapping power strokes its a question separating which overlapping power stroke is the cause of the misfire. Easy on a 4 cylinder much harder on a 12 cylinder. Also the ECU to ECU communication speed may be an issue if that's involved in the relevant cylinders

I can't back this up with a citation, but I believe on at least some dual ECU applications, one of them takes responsibility for all misfire detection.

 

[dn242]

The injector cleaning shop forgot to fudge the "after" static flows to make them more believable What is injector "N"?
Thank you for making the effort to write a feedback post!

That is just bad handwriting for injector "#4", which was the failed injector :-)

agree its probably not a question of ECU processing speed or capability but with the overlapping power strokes its a question separating which overlapping power stroke is the cause of the misfire. Easy on a 4 cylinder much harder on a 12 cylinder. Also the ECU to ECU communication speed may be an issue if that's involved in the relevant cylinders

@RGH0 I thought the same thing that the cylinder misfire detection on the cylinder before the 'problem' cylinder could be misidentified due to the noisiness of the input data. But my knowledge in this area is waaaay less than @Dr Sheldon so I don't actually have anything to back this up.

I did replace all plugs and coils at the same time as the injector cleaning, so it's possible that a coil/plug could have contributed to an additional issue on #11. Once the engine was reassembled and reset there were no misfires detected in any cylinders, so some combination of those variables cured the misfire problem. In any event I'm grateful for the help from everyone, or I wouldn't have even known where to start.

 

[Dr Sheldon]

agree its probably not a question of ECU processing speed or capability but with the overlapping power strokes its a question separating which overlapping power stroke is the cause of the misfire. Easy on a 4 cylinder much harder on a 12 cylinder.

Not at all !!

Really no harder on a 12 Cylinder.

I Use a Pico Automotive Oscilloscope and looking at cylinder contribution on a 12 cylinder at 4000rpm is a walk in the park for it !!

It is more than capable !!! If you have not had the pleasure of using that tool it may be difficult for you to imagine how powerful it is.

The thing can take 60 million samples in one second !!


Those Ignition events do not overlap, they are 60 degrees apart - Even at 4000 rpm that is a very long time in modern electronic monitoring ??

 

[Dr Sheldon]

I Use a Pico Automotive Oscilloscope and looking at cylinder contribution on a 12 cylinder at 4000rpm is a walk in the park for it !!

It is more than capable !!! If you have not had the pleasure of using that tool it may be difficult for you to imagine how powerful it is.

Those ECU's even as a pair, allowing time for them to gather data -- then share data between them, are not getting confused or misreporting anything !!

 

[RGH0]

Those ECU's even as a pair, allowing time for them to gather data -- then share data between them, are not getting confused or misreporting anything !!

It would be nice to see the crank acceleration curve data on a 12 cylinder engine to see how easy it is to detect an individual cylinder miss fire and automatically allocate it to one cylinder with the overlap power strokes.. just asking as collecting the data I am sure is possible with the right instruments but automatically allocating it to a specific cylinder does not strike me as being easy on a 12 cylinder engine

 

[Dr Sheldon]

It would be nice to see the crank acceleration curve data on a 12 cylinder engine to see how easy it is to detect an individual cylinder miss fire and automatically allocate it to one cylinder with the overlap power strokes.. just asking as collecting the data I am sure is possible with the right instruments but automatically allocating it to a specific cylinder does not strike me as being easy on a 12 cylinder engine

Easy Peesy

If you are in the UK ever - Bring me a V12 or even a Bugatti W16, I will hook it up to a scope and demonstrate.

Dare I say that you will be blown away by the clarity and the accuracy ! Just as I was once.

Alternatively get your self a Pico, or even a demonstration from your local distributer and see for yourself !