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

[dn242]

First, thank you to the VCDS team for developing such an amazing tool. I'm new to VCDS and CAN-based systems (carburetors are more my thing) so I'm hoping for help to determine whether the problem below is a simple misfire problem (plugs/coils), something worse, or whether I should run from this car as a maintenance money pit.

I just accepted delivery of a 2014 Flying Spur W12 Base. The car has been driven (by me) fewer than 25 miles. The car has 32K miles and has not had its 30K maintenance, which would include new spark plugs and coils. The car is single-owner with clean, single-dealer maintenance history from 0 to ~18K miles (unable to get maintenance records beyond that).

History:

• Had a reputable European-specialist shop do a Pre-Purchase Inspection where they supposedly scanned the car and it passed with 'no issues' (suspect).
• Car delivered to me (trailered), next morning I drove it to a state inspection station. While sitting in line the "check engine" light came on.
• Car failed inspection because of the check engine code P0304: Cylinder 4 Misfire Detected.
• VCDS scan done (below); cylinder misfires identified.
• Realtime monitoring shows mostly low-RPM misfires (few or no misfires under hard acceleration or highway driving)
  • I only have ~10 miles of data on this right now.

Question 1: From the VCDS scan below it appears that Cylinder 4 has a long history of misfires (counter is maxed out). Cylinders 9 and 11 were also observed to misfire during driving. Most (all? still reviewing logs) misfires seem to occur during idle or low-speed, low-throttle driving. What should the next diagnostic steps be for misfire testing? Fuel pressure test?

Question 2: The car was involved in a minor collision a few years ago and there was a repair on the door. Are the 46-Central Conv. instrument failures and one-wire CAN warning potential electrical gremlins? Are these reasonable to trace/solve?

According to the Bentley service manual the diagnostic steps for Cylinder Misfire P0304 code is:

• Check fuel injectors.
• Check ignition coil with power output.
• Check spark plugs.
• Check for engine mechanical fault by performing a cylinder pressure test.

It is non-trivial to change the coils and plugs on a W12, so before tearing the top off the engine I'd appreciate any diagnostic help that might help pinpoint the issue.

FULL SCAN

Monday,01,July,2024,16:04:46:46110
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 24.5.0.0 (x64)  HEX-V2 CB: 0.4643.5
Data version: 20240429 DS355.0
www.Ross-Tech.com


VIN:                                     License Plate: 14FLYINGSPUR
Mileage: 51360km-31913mi   Repair Order: INITIAL-SCAN



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Chassis Type: ZA-BY62 (6N0)
Scan: 01 02 03 05 06 07 08 09 11 31 15 16 17 19 28 2E 34 36 37 38
          46 47 48 53 56 5D 65 66 68 6C 6D 71 76 77

VIN:                                     Mileage: 51360km-31913miles

01-Engine -- Status: Malfunction 0010
02-Auto Trans -- Status: OK 0000
03-ABS Brakes -- Status: OK 0000
04-Steering Angle -- Status: OK 0000
05-Acc/Start Auth. -- Status: OK 0000
06-Seat Mem. Pass -- Status: OK 0000
07-Control Head -- Status: OK 0000
08-Auto HVAC -- Status: OK 0000
09-Cent. Elect. -- Status: OK 0000
11-Engine II -- Status: Malfunction 0010
31-Engine other -- Status: Malfunction 0010
15-Airbags -- Status: OK 0000
16-Steering wheel -- Status: OK 0000
17-Instruments -- Status: Malfunction 0010
19-CAN Gateway -- Status: Malfunction 0010
28-HVAC, Rear -- Status: OK 0000
2E-Media Player 3 -- Status: OK 0000
34-Level Control -- Status: OK 0000
36-Seat Mem. Drvr -- Status: Malfunction 0010
37-Navigation -- Status: OK 0000
38-Roof Electronics -- Status: OK 0000
42-Door Elect, Driver -- Status: OK 0000
46-Central Conv. -- Status: Malfunction 0010
47-Sound System -- Status: OK 0000
48-Seat, Rear, DS -- Status: OK 0000
52-Door Elect, Pass. -- Status: OK 0000
53-Parking Brake -- Status: OK 0000
56-Radio -- Status: OK 0000
5D-Operations -- Status: OK 0000
62-Door, Rear Left -- Status: Malfunction 0010
65-Tire Pressure -- Status: OK 0000
66-Seat, Rear -- Status: OK 0000
68-Wiper Electr. -- Status: OK 0000
6C-Back-up Cam. -- Status: OK 0000
6D-Trunk Elect. -- Status: OK 0000
71-Battery Charger -- Status: OK 0000
72-Door, Rear Right -- Status: OK 0000
76-Park Assist -- Status: OK 0000
77-Telephone -- Status: OK 0000
-------------------------------------------------------------------------------
Address 01: Engine (J623-CKHF)       Labels: None
   Part No SW: 07C 906 023 K    HW: 07C 907 309
   Component: ME17.1.6      H16 6514 
   Revision: MHH16---    Serial number: VWX3Z0M7015417 CVN: 25C7EB5B
   Coding: 0D2A0032432E00020001
   Shop #: WSC 60290 001 1048576
   ASAM Dataset: EV_ECM60TMP11107C906023K 001004
   ROD: EV_ECM60TMP07C906023K.rod
   VCID: 290824D0297263A220D-807C
   VINID: 8D34954C9A911554C0241149103A31ABBB

3 Faults Found:
16672 - Please Check DTC Memory of ECU Number 2
          P1923 00 [00101111] - -
          Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Priority: 2
                    Fault Frequency: 3
                    Mileage: 51358 km
                    Date: 2024.07.01
                    Time: 13:30:00

                    Engine RPM: 587.50 /min
                    Normed load value: 18.0 %
                    Vehicle speed: 0 km/h
                    Coolant temperature: 101 °C
                    Intake air temperature: 81 °C
                    Ambient air pressure: 1010 mbar
                    Voltage terminal 30: 14.512 V
                    Unlearning counter according OBD: 40

10203 - Random/Multiple Cylinder Misfire Detected
          P0300 00 [01100001] - -
          Not Confirmed - Tested Since Memory Clear

10594 - ROD - Unknown Error Code
          - 00 [01100001]
          Not Confirmed - Tested Since Memory Clear

Readiness: 0010 0001

-------------------------------------------------------------------------------
Address 02: Auto Trans (J217)       Labels:* None
   Part No SW: 4W0 927 158 A    HW: 0CU 927 760 A
   Component: OBL 60 MPIUSA H16 0005 
   Revision: --H16---    Serial number: VWX3Z0M7015417 CVN: AEB9E0B9
   Coding: 000002
   Shop #: WSC 60290 001 1048576
   ASAM Dataset: EV_TCMAL450211 002010
   ROD: EV_TCMAL450211_BY62.rod
   VCID: 3C26ED84D6E0E60A4BB-8068

No fault code found.

-------------------------------------------------------------------------------
Address 03: ABS Brakes        Labels: None
   Part No SW: 4W0 614 517 A    HW: 4W0 614 517 A
   Component: ESP 8.1 4WD     H01 1100 
   Revision: 00000000    Serial number: 00000000000000
   Coding: 0002543
   Shop #: WSC 00083 790 00197
   VCID: 3436C5A4F2702E4A83B-8060

No fault code found.

-------------------------------------------------------------------------------
Address 05: Acc/Start Auth.        Labels: 3D0-909-13x-05.lbl
   Part No SW: 3D0 909 137 G    HW: 3D0 909 137 G
   Component: C0 Kessy            6850 
   Revision: 00H24072    Serial number: VWX3Z0M7015417
   Coding: 0405741
   Shop #: WSC 00083 790 00190
   VCID: 2B04DED82F4E71B2D21-807E

   Subsystem 1 - Part No: XXXXXXXXXXX
   Component: ELV                 XXXX

No fault code found.

-------------------------------------------------------------------------------
Address 06: Seat Mem. Pass (J521)       Labels: None
   Part No SW: 4W0 959 760     HW: 4W0 959 760
   Component: MEM-BFS       H04 0600 
   Revision: AA000000    Serial number: 00000077608911
   Coding: D0081F0085070090090001010101002100012727000000
   Shop #: WSC 00083 790 00242
   VCID: 7F5CDA8887B63D122E9-802A

No fault code found.

-------------------------------------------------------------------------------
Address 07: Control Head        Labels: 3D0-907-048.clb
   Part No SW: 3D0 907 048     HW: 3D0 907 048
   Component: J127 KBT vorn       0100 
   Revision: ABH30001    Serial number: VWZ6Z7U0044003
   Shop #: WSC 00000 000 00000
   VCID: 639476F8071EF9F22A1-8036

No fault code found.

-------------------------------------------------------------------------------
Address 08: Auto HVAC        Labels: None
   Part No: 3W5 907 040 J
   Component: Climatronic BY621   3029 
   Coding: 0000101
   Shop #: WSC 00083 790 00190
   VCID: 3D20E080C13AEF027C5-8068

No fault code found.

-------------------------------------------------------------------------------
Address 09: Cent. Elect.        Labels:. 3D0-937-049-V2.clb
   Part No SW: 3D0 937 049 Q    HW: 3D0 937 049 Q
   Component: J519                7700 
   Revision: -4007---    Serial number: --------------
   Coding: 40820000AB2A11C02508030000000000
   Shop #: WSC 00083 790 00190
   VCID: 382EF194EE18CA2AAF3-806C

No fault code found.

-------------------------------------------------------------------------------
Address 11: Engine II (J624)       Labels: None
   Part No SW: 07C 906 023 K    HW: 07C 907 309
   Component: ME17.1.6      H16 6514 
   Revision: MHH16---    Serial number: VWX3Z0M7015417 CVN: 25C7EB5B
   Coding: 0D2A0032432E00020001
   Shop #: WSC 60290 001 1048576
   ASAM Dataset: EV_ECM60TMP21107C906023K 001004
   ROD: EV_ECM60TMP07C906023S.rod
   VCID: 290824D0297263A220D-807C

2 Faults Found:
12646 - Random/Multiple Cylinder Misfire Detected
          P0300 00 [11101101] - -
          MIL ON - Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Priority: 2
                    Fault Frequency: 1
                    Mileage: 51358 km
                    Date: 2024.07.01
                    Time: 13:28:26

                    Engine RPM: 598.00 /min
                    Normed load value: 17.6 %
                    Vehicle speed: 0 km/h
                    Coolant temperature: 101 °C
                    Intake air temperature: 77 °C
                    Ambient air pressure: 1010 mbar
                    Voltage terminal 30: 14.277 V
                    Unlearning counter according OBD: 40

10594 - Cylinder 4
          P0304 00 [11101101] - Misfire Detected
          MIL ON - Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Priority: 2
                    Fault Frequency: 1
                    Mileage: 51358 km
                    Date: 2024.07.01
                    Time: 13:30:00

                    Engine RPM: 598.00 /min
                    Normed load value: 17.6 %
                    Vehicle speed: 0 km/h
                    Coolant temperature: 101 °C
                    Intake air temperature: 77 °C
                    Ambient air pressure: 1010 mbar
                    Voltage terminal 30: 14.277 V
                    Unlearning counter according OBD: 40


-------------------------------------------------------------------------------
Address 15: Airbags        Labels: None
   Part No SW: 3W3 959 655     HW: 3W3 959 655
   Component: 27 Airbag 9.43  H04 0050 
   Revision: 93H04005    Serial number: 003FV000HH1+ 
   Coding: 0012855
   Shop #: WSC 00083 790 00190
   VCID: 04565564E2505ECA73B-8050

   Subsystem 1 - Part No: 4W0 959 339
   Component: BF-Gewichtsens. H03 0102

   Subsystem 2 - Serial number: 02T65         

   Subsystem 3 - Serial number: 0001.01.0000H0300000000000ÿ†63

   Subsystem 4 - Serial number: 000000ÿ†6332DRB40F3E4E2C4ÿ†63

   Subsystem 5 - Serial number: E4E2C4ÿ†6342DRB40F340F16Sÿ†63

   Subsystem 6 - Serial number: 40F16Sÿ†63528RB406FEB45C4ÿ†63

   Subsystem 7 - Serial number: EB45C4ÿ†63628RB406FEA481$ÿ†63

   Subsystem 8 - Serial number: EA481$ÿ†63747RB40702A570Eÿ†63

   Subsystem 9 - Serial number: 2A570Eÿ†63847RB40702A373Gÿ

   Subsystem 10 - Serial number: 2A373Gÿ

No fault code found.

-------------------------------------------------------------------------------
Address 16: Steering wheel        Labels: 7L6-953-549.lbl
   Part No: 7L6 953 549 K
   Component: J527                3601 
   Coding: 0000032
   Shop #: WSC 00083 790 00190
   VCID: 47CC826893E6B5D2D69-8012

No Faults Found
  or DTCs not supported by controller
  or a communication error occurred

-------------------------------------------------------------------------------
Address 17: Instruments        Labels: 3Wx-920-xxx-17.clb
   Part No SW: 3W0 920 851 L    HW: 3W0 920 851 L
   Component: J285 KOMBI-INST.    3925 
   Revision: KPH10V02   
   Coding: 0034214
   Shop #: WSC 19178 004 1048576
   VCID: 3FDC9A88CB76FD126E9-806A

1 Fault Found:
00470 - Company Comfort Databus in Single Wire
            011 - Open Circuit - Intermittent
             Freeze Frame:
                    Fault Status: 00101011
                    Fault Priority: 2
                    Fault Frequency: 4
                    Reset counter: 16
                    Mileage: 51334 km
                    Time Indication: 0
                    Date: 2024.06.20
                    Time: 00:00:05


-------------------------------------------------------------------------------
Address 19: CAN Gateway        Labels:. 6N0-909-901-7L.clb
   Part No SW: 6N0 909 901     HW: 3W0 920 851 L
   Component: J533  GW-K-CAN TP20 3925 
   Coding: 5FFAFFFFEB551702
   Shop #: WSC 19178 004 1048576
   VCID: 70BE09B4C6A8526AA73-8024

1 Fault Found:
00470 - Company Comfort Databus in Single Wire
            011 - Open Circuit - Intermittent
             Freeze Frame:
                    Fault Status: 00101011
                    Fault Priority: 2
                    Fault Frequency: 4
                    Reset counter: 16
                    Mileage: 51334 km
                    Time Indication: 0
                    Date: 2024.06.20
                    Time: 00:00:05


-------------------------------------------------------------------------------
Address 28: HVAC, Rear (J524)       Labels: None
   Part No SW: 4W0 035 008     HW: 4W0 035 008
   Component: CLIMATE ECU   H06 0062 
   Revision: P1H06004    Serial number: 51300129127001
   Coding: 00000000010102
   Shop #: WSC 00000 000 00000
   VCID: 6B841ED8E3CEB1B2921-803E

   Subsystem 1 - Part No SW: 4W0 907 042 A    HW: 4W0 907 042
   Component: RBM-BY621  H09 0055
   Serial number: WA107362000004944476

No fault code found.

-------------------------------------------------------------------------------
Address 2E: Media Player 3 (J650)       Labels:. 5N0-035-342.lbl
   Part No SW: 5N0 035 342 G    HW: 5N0 035 342 G
   Component: SG EXT.PLAYER H19 0770 
   Revision: A1001003    Serial number: 7665317695   
   Coding: 030100
   Shop #: WSC 00083 790 00191
   VCID: 2B04DED8230E71B2D21-807E

No fault code found.

-------------------------------------------------------------------------------
Address 34: Level Control        Labels: None
   Part No: 4W0 907 553
   Component: LUFTFDR.-CDC- 3C3V0 7705 
   Coding: 0005541
   Shop #: WSC 00083 790 00171
   VCID: 78AE3194AE980A2A6F3-802C

No fault code found.

-------------------------------------------------------------------------------
Address 36: Seat Mem. Drvr (J136)       Labels: None
   Part No SW: 4W0 959 760     HW: 4W0 959 760
   Component: MEM-FS        H04 0600 
   Revision: AA000000    Serial number: 00000077600982
   Coding: D0081F0085870090090001010101012100012727000000
   Shop #: WSC 00083 790 00236
   VCID: 7F5CDA8887B63D122E9-802A

1 Fault Found:
03341 - Ventilator for Back Rest
            009 - Open or Short to Ground
             Freeze Frame:
                    Fault Status: 01101001
                    Fault Priority: 3
                    Fault Frequency: 1
                    Reset counter: 227
                    Mileage: 51344 km
                    Time Indication: 0
                    Date: 2024.06.24
                    Time: 13:45:23


-------------------------------------------------------------------------------
Address 37: Navigation (J0506)       Labels:. 3D0-035-680.clb
   Part No SW: 3W0 035 017 Q    HW: 3W0 035 017 Q
   Component: RNS-MID       H32 0584 
   Revision: AB001001    Serial number: VWZ6Z7U0044003
   Coding: 06010002000000044000
   Shop #: WSC 53978 001 1048576
   VCID: 3B24EE98D36EE132421-806E

   Subsystem 1 - Part No: 3W0 919 859 BN
   Component: NAR V4  7963

No fault code found.

-------------------------------------------------------------------------------
Address 38: Roof Electronics        Labels: None
   Part No: 3W0 907 135 H
   Component: Dachmodul           0910 
   Coding: 0020493
   Shop #: WSC 00083 790 00197
   VCID: 3B24EE98DF2EE132421-806E

No fault code found.

-------------------------------------------------------------------------------
Address 46: Central Conv.        Labels: 3D0-959-933.clb
   Part No: 4W0 959 794
   Component: TSG HR        D26   
   Coding: 0000040
   Shop #: WSC 00000 790 00190
   VCID: 06524F6CD43C6CDA6DF-4B30

   Subsystem 1 - Part No: 4W0 959 107 A
   Component: 11 HDSG             0806

   Subsystem 2 - Part No: 7L0 907 719 A
   Component:    Neigungssensor   0020

3 Faults Found:
00668 - Supply Voltage Terminal 30
            002 - Lower Limit Exceeded - Intermittent
00470 - Company Comfort Databus in Single Wire
            011 - Open Circuit - Intermittent
00122 - Outside Warning Light/Door Exit Light; Rear Left
            012 - Electrical Fault in Circuit

-------------------------------------------------------------------------------
Address 47: Sound System        Labels: None
   Part No SW: 4W0 035 465     HW: 4W0 035 465
   Component: DSP 10 Kanal        0010 
   Revision: 00H07001    Serial number: 75824010584903
   Shop #: WSC 00000 000 00000
   VCID: 72BA03BCC8A4607A517-8026

No fault code found.

-------------------------------------------------------------------------------
Address 48: Seat, Rear, DS
Cannot be reached

-------------------------------------------------------------------------------
Address 53: Parking Brake        Labels: 3W0-907-801.clb
   Part No SW: 3W0 907 801 H    HW: 3W0 907 801 H
   Component: EPB  BC7H0300   HC7 0300 
   Coding: 0022513
   Shop #: WSC 00083 790 00197
   VCID: 3B24EE98DF7EE132421-5160

No fault code found.

-------------------------------------------------------------------------------
Address 56: Radio (J0506)       Labels:. 3D0-035-680.clb
   Part No SW: 3W0 035 017 Q    HW: 3W0 035 017 Q
   Component: RNS-MID       H32 0584 
   Revision: AB001001    Serial number: VWZ6Z7U0044003
   Coding: 06010002000000044000
   Shop #: WSC 53978 001 1048576
   VCID: 3B24EE98D36EE132421-806E

   Subsystem 1 - Part No: 3W0 919 859 BN
   Component: NAR V4  7963

No fault code found.

-------------------------------------------------------------------------------
Address 5D: Operations
Cannot be reached

-------------------------------------------------------------------------------
Address 65: Tire Pressure        Labels: None
   Part No SW: 3W7 907 273 C    HW: 3W7 907 273 C
   Component: J0502 RDK           0006 
   Revision: 0004 006    Serial number: 00000600003270
   Coding: 0000E03175CA4286EB75B9FD52EB0097FC004B6E4B6E4B6E4B6E4B64
   Shop #: WSC 00083 790 00170
   VCID: 40DE9974B6C882EA173-8014

No fault code found.

-------------------------------------------------------------------------------
Address 66: Seat, Rear (J877)       Labels: None
   Part No SW: 4W0 959 760     HW: 4W0 959 760
   Component: MEM-BFS-Fond  H04 0600 
   Revision: AA000000    Serial number: 00000077591139
   Coding: C0081E8085810000090021000001000000002727000000
   Shop #: WSC 00083 790 00190
   VCID: 7F5CDA8887B63D122E9-802A

No fault code found.

-------------------------------------------------------------------------------
Address 68: Wiper Electr.        Labels: 3Wx-955-023.clb
   Part No: 3W5 955 023 M
   Component: Wischermodul       ª0401 
   Shop #: WSC 00000 725 65552
   VCID: 44D69564A2D09ECA33B-8010

No fault code found.

-------------------------------------------------------------------------------
Address 6C: Back-up Cam.        Labels: None
   Part No SW: 4W0 907 441     HW: 4W0 907 441
   Component: J772__Rearview      0030 
   Revision: 00H13000    Serial number: 525 PA8J390256
   Coding: 2020003
   Shop #: WSC 00083 790 00171
   VCID: 74B605A4B2B06E4A43B-8020

No fault code found.

-------------------------------------------------------------------------------
Address 6D: Trunk Elect. (----)       Labels:| 7N0-959-107.clb
   Part No SW: 4W0 959 107 A    HW: 4W0 959 107 A
   Component: HDSG-Modul    H04 0806 
   Revision: 00000000    Serial number: 282300145 Dataset Number: V03935176YS 0002
   Coding: 170206C120
   Shop #: WSC 00083 790 00190
   ASAM Dataset: EV_HDSGBY621 001002
   ROD: EV_HDSGBY621.rod
   VCID: 3B24EE98D3EEE132421-806E

No fault code found.

-------------------------------------------------------------------------------
Address 71: Battery Charger (J367)       Labels:* None
   Part No SW: 3W3 915 181 B    HW: 3W3 915 181 B
   Component: EMM Batt Man  H05 0570 
   Serial number: 0000000001
   Coding: 5E0100
   Shop #: WSC 00083 790 00211
   ASAM Dataset: EV_BatteChargVaria1 002019
   ROD: EV_BatteChargVaria1_002.rod
   VCID: 382EF194E2D8CA2AAF3-806C

   Battery Monitoring Control Module:
   Subsystem 1 - Part No SW: 8K0 915 181 C    HW: 8K0 915 181 C
   Component: J367-BDM  H07 0141
   Serial number: 40278911091041200900

No fault code found.

-------------------------------------------------------------------------------
Address 76: Park Assist        Labels: 3W0-919-283-V3.clb
   Part No SW: 3W0 919 283 G    HW: 3W0 919 283 E
   Component: J446  ST Parkhilfe  0111 
   Revision: 11H02001    Serial number: 58131326600692
   Coding: 0300066
   Shop #: WSC 00083 790 00190
   VCID: 41D89C70BDC28BE218D-8014

No fault code found.

-------------------------------------------------------------------------------
Address 77: Telephone (J412)       Labels:| 3C8-035-730-A.clb
   Part No SW: 3D0 035 730 B    HW: 3D0 035 730 B
   Component: Telefon       012 0825 
   Revision: --------    Serial number: 35909603571978
   Coding: 020106010100010000000000
   Shop #: WSC 00083 790 00191
   ASAM Dataset: EV_UHVPremi A02705
   ROD: EV_UHVPremi_A02.rod
   VCID: 1B640E18732E8132A21-804E

No fault code found.

End----------(Elapsed Time: 03:16, VBatt start/end: 12.2V/12.2V)-----------

I am in the process of gathering realtime log data related to misfires and it appears that Cylinders 4,9, and 11 (mostly Cyl 4) have intermittent failures while running.
Total misfire count shows that Cylinder 4 is *maxed out* on misfire count.

MISFIRE TOTAL COUNT REPORT

Monday,01,July,2024,16:30:16:46110
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 24.5.0.0 (x64)  HEX-V2 CB: 0.4643.5
Data version: 20240429 DS355.0
www.Ross-Tech.com


VIN:                                   License Plate: 14FLYINGSPUR
Mileage:    Repair Order: INITIAL-TEST


                Address 11: Engine II  (07C 906 023 K)

16:30:00
  IDE01975   Numb.of misfir.: cylinder 1 3288 
  IDE01976   Numb.of misfir.: cylinder 2 541 
  IDE01977   Numb.of misfir.: cylinder 3 290 
  IDE01978   Numb.of misfir.: cylinder 4 65535 
  IDE03363   Numb.of misfir.: cylinder 5 902 
  IDE03364   Numb.of misfir.: cylinder 6 7980 
  IDE03365   Numb.of misfir.: cylinder 7 2745 
  IDE03366   Numb.of misfir.: cylinder 8 1011 
  IDE03367   Numb.of misfir.: cylinder 9 12537 
  IDE03368   Numb.of misfir.: cylinder 10 230 
  IDE03369   Numb.of misfir.: cylinder 11 2660 
  IDE03370   Numb.of misfir.: cylinder 12 852

 

[Ziddywerks]

Swap coil to a different cylinder and swap plug to a different cylinder than the coil see if misfire follows plug or coil. Replace as needed. if issue remains on cyl#4 cylinder leak down is recommended.

 

[dn242]

@EuroX thanks for the help! To access the coil packs and spark plugs on the W12 requires complete removal of the intake manifold and attached assemblies. The only way to test cylinder operation would be to reassemble the manifold (new gasket, etc) and test drive.

Do you have any experience with a leak down test for the W12? It's so much work to get to the coils/plugs that a leak down / compression test would be easy relative to reassembling the entire manifold. Can you crank a W12 to get a cylinder to TDC for testing?

 

[Ziddywerks]

@EuroX thanks for the help! To access the coil packs and spark plugs on the W12 requires complete removal of the intake manifold and attached assemblies. The only way to test cylinder operation would be to reassemble the manifold (new gasket, etc) and test drive.

Do you have any experience with a leak down test for the W12? It's so much work to get to the coils/plugs that a leak down / compression test would be easy relative to reassembling the entire manifold. Can you crank a W12 to get a cylinder to TDC for testing?

I don't believe that's accurate you only need to remove the black engine covers/kidneys to gain access to the plugs and coils.

 

[jyoung8607]

It looks scarier than it really is. I've done it several times on my Phaeton W12. The intake setup isn't precisely the same, but just glancing at a picture, it seems almost certain that both sides can be detached from the center/lower intake assembly. Obviously you'll need to disconnect the throttle bodies and various vacuum stuff.

You already know you're overdue for plugs, which is a potential contributor. Do that, and while you're doing it, label all the coilpacks coming out and make sure the #4 coilpack gets swapped with another cylinder. Takes care of overdue maintenance and accomplishes two different diagnostic tests at the same time. I'd do that before worrying about other tests.

 

[dn242]

I don't believe that's accurate you only need to remove the black engine covers/kidneys to gain access to the plugs and coils.

@EuroX I'm searching in the Bentley manual for the procedure now, but everything I've seen online requires that the intake manifold be removed to gain access to the coils/plugs.
NEW: In looking closer at these videos (e.g. GT 6.0L Spark Plug Replacement and W12 Spark Plug Replacement) it looks like most of the plugs are accessible without complete manifold removal. If that's true it would be amazing. I think only cylinders 1/2/7/8 might be blocked.

I'm trying to figure out here whether there is a way to diagnostically rule out anything before either trying to send the car back to the seller or start a teardown. I'll go check now. I appreciate the help and response!

 

[dn242]

It looks scarier than it really is. I've done it several times on my Phaeton W12. The intake setup isn't precisely the same, but just glancing at a picture, it seems almost certain that both sides can be detached from the center/lower intake assembly. Obviously you'll need to disconnect the throttle bodies and various vacuum stuff.

You already know you're overdue for plugs, which is a potential contributor. Do that, and while you're doing it, label all the coilpacks coming out and make sure the #4 coilpack gets swapped with another cylinder. Takes care of overdue maintenance and accomplishes two different diagnostic tests at the same time. I'd do that before worrying about other tests.

@jyoung8607 Thanks! When you were working on your W12 did you ever see this type of misfire problem (that I mentioned in the original post)? Or was your work on coils and plugs just for routine/preventative maintenance?

 

[jyoung8607]

I've done three rounds of plugs, by-the-book scheduled PM (40k, 80k, 120k) and some diagnostics that didn't involve misfires.

Looking at the videos above, it looks like the Bentley move is to lift both sides and the center as an assembly, and leave the lower. Not unreasonable. That said, if you have an open option to return to the seller and are just looking to check some easy stuff, I agree it looks like you can trivially access #4. I actually have to pull at least the sides off my intake manifold to access any coil/plug assemblies at all.

 

[jyoung8607]

BTW, since this model-year appears to have direct injection and you can see fuel pressure readings in diagnostics, do go ahead and check that.

If fuel pressure is too low under idle and low-load conditions but is good under load, you might be losing one of your fuel pumps. I'm guessing even with the change to DI, you might still have two separate low-pressure pumps in the fuel tank. Sometimes Phaetons would have a similar problem where the primary pump dies (which runs all the time) but the secondary pump still works (which runs only at start, and under high load, and I think if the fuel level is low). If you see signs of low fuel pressure only at low load, you can trivially check that by bypassing the secondary fuel pump relay. If the car suddenly works fine with the secondary fuel pump running all the time, you have your answer.

 

[dn242]

@jyoung8607 Had not occurred to me that it could also be a fuel pump issue. Thanks so much for the tips - I really do appreciate it! I will do as you suggest this evening to troubleshoot further and update later.

 

[dn242]

@EuroX Thanks for the suggestion on removing the air intakes. It is correct that you can access the coils/plugs on Cylinders 4/5/6 and 9/10/11/12 without removing the manifold or fuel rails. Thankfully the problem cylinders in my case are all accessible!

@jyoung8607 I can only find one fuel-pressure value in VCDS for this car, but in monitoring the fuel pressure while driving it seemed consistent. I have not yet attempted to check fuel pump relays (still reviewing the Bentley service manual for this).

Testing Update (procedure: make change, reassemble and drive, record values):

1. Fuel pressure test - no leaks (fuel pressure rose continuously over 1 hour post-shutdown).
2. Swapped coils - no change in misfires (remained in cyl 4/9/11).
3. Swapped plugs - no change in misfires (remained in cyl 4/9/11).
   1. There were two misfires in other cylinders on this test, but there were 30-500 misfires in the problem cylinders, so I don't think plugs are the problem.
   2. The gaps on several of the plugs were wider than spec but nothing was changed for the test.

Conclusion: Misfires persist in Cylinders 4/9/11 and appear at idle or low-speed + low-throttle conditions.

I have not yet tested the fuel injectors. Unfortunately I can't find any sensor options in VCDS that provide fuel injector data points. Does anyone know if there are relevant injector data outputs in this W12 that can be accessed in VCDS? If not then pulling the injectors is required :-/

At this point I don't have the tools and W12 Bentley knowledge needed to complete a compression / leakdown test, so I am reaching out to some local mechanics with Bentley experience to try and diagnose further. If anyone has any ideas or suggestions they are most appreciated and welcome.

 

[Ziddywerks]

If misfires have not moved it would be wise to perform leak down test or compression test. Also probably wise to put 10ml of oil down each affected cylinder just in case they are washed out from misfires.

 

[Dr Sheldon]

At this point I don't have the tools and W12 Bentley knowledge needed to complete a compression / leakdown test, so I am reaching out to some local mechanics with Bentley experience to try and diagnose further. If anyone has any ideas or suggestions they are most appreciated and welcome.

That is possibly not what you need - They are great at nuts, bolts and replacing bits but Diagnosticians in the art of taking accurate measurements Non Intrusively with Diagnostic value they are not !!

This where an oscilloscope and amp clamps would be useful.

Measure starter current with fuel disabled will give you cylinder relative compression - 10 minutes !!
Amp Clamp around the common power supply (possibly one bank at a time and monitor current draw of each coil - A bad coil will stick out like a saw thumb - as will any compression issue !! - Another 10 minutes - Job Done !!

 

[dn242]

That is possibly not what you need - They are great at nuts, bolts and replacing bits but Diagnosticians in the art of taking accurate measurements Non Intrusively with Diagnostic value they are not !!

This where an oscilloscope and amp clamps would be useful.

Measure starter current with fuel disabled will give you cylinder relative compression - 10 minutes !!
Amp Clamp around the common power supply (possibly one bank at a time and monitor current draw of each coil - A bad coil will stick out like a saw thumb - as will any compression issue !! - Another 10 minutes - Job Done !!

@Dr Sheldon Thanks so much for the tips. I myself fall into the 'wrench-swinging' category (the cars I normally work on don't have CAN Bus issues because they don't have CAN sensors). I talked to the shop about a relative compression test and they are going to try it today.

 

[dn242]

I ended up taking the car to a European / Audi specialist last week and as of today they've tested but are still not able to definitively find the problem.

Update from mechanic:

1. Smoke test on all vacuum lines - no leaks observed anywhere.
   1. "Full air intake setup confirmed to have no leaks."
2. Cracked seal on oil dipstick tube causing air leak (already known).
   1. "When we plugged the oil dipstick tube the lean condition faults transferred from Bank 2 to Bank 1."
3. Common ground locations checked for continuity (pass).
   1. When they initially started the car for diagnostics they observed no misfires. I asked them to drive the car, and after they were able to observe some misfires. The lead mechanic said he saw something similar on a Mercedes where a bad ground was connecting intermittently to the chassis, causing random misfires. I don't think they checked all the grounds in the car, but at least the ones near the fuel pumps and engine bay appear to be properly connected.

Current state:
The 'best guess' from the mechanic is that Injector #4 is bad and needs to be replaced. He wants to move Injector #4 to another cylinder to verify. The problem is that labor costs for this are higher than simply replacing the injector (the manifold and fuel rails need to be removed / replaced, then if the injector is bad they are removed/replaced again). The injector replacement might fix the misfires on Cylinder 4, but Cyl 9 and 11 also have (fewer) misfires so replacing #4 injector won't help with 9 and 11.

New testing by mechanic:
@jyoung8607 Your idea about testing the fuel pumps is next in line here. I asked them to try and test the fuel pumps to see if they can find any faults. @Dr Sheldon I also asked the shop to do a relative compression test and report the results. The mechanic did say they listened to the top end and heard nothing that sounded like a bad/sticking valve and in his experience he's never seen a valve failure on the W12 (but they also still can't find the problem).

 

[Dr Sheldon]

This where an oscilloscope and amp clamps would be useful.

Measure starter current with fuel disabled will give you cylinder relative compression - 10 minutes !!
Amp Clamp around the common power supply (possibly one bank at a time and monitor current draw of each coil - A bad coil will stick out like a saw thumb - as will any compression issue !! - Another 10 minutes - Job Done !!

Look like they are incapable of all of the above !!

I talked to the shop about a relative compression test and they are going to try it today.

It takes 10 minutes and from that reply they have no clue what a Relative Compression Test is ??

Cracked seal on oil dipstick tube causing air leak (already known).

1. "When we plugged the oil dipstick tube the lean condition faults transferred from Bank 2 to Bank 1."

Why dont you Replace the tube first ??

 

[Dr Sheldon]

The type of testing I refer to: Using an oscilloscope with accessories to look at Current, Compression, Temperature, Pressure with Math Channels to look at RPM for each piston as it is fired - more accurately the rate of acceleration & speed of each piston so that the slightest misfire can be seen long before the ECU will report it !!

Be sure none of this is taught to Qualified Master Technicians at your Bentley Dealership - or any other dealership anywhere in the world !! Hence they get it wrong a lot !!

I am a Bosch Trained, Qualified Master Tech and they dont teach at this level !!

Few and far between are people like me that have gone above and beyond to train and learn to this level and continue to learn at our own expense and time.

With the right equipment which I have - Your fault could be nailed in half a day !! Biggest ballache of the Bentley is access to components. Other than that it is not a difficult vehicle to work on, Fairly straight forward technology !!

 

[dn242]

@Dr Sheldon I appreciate the help and comments. I'll definitely follow up more forcefully with the shop to see what they're capable of. And if you know of anyone in Houston, TX that you would trust or recommend for diagnosis it would be most welcome. I'm learning a lot myself searching online based on your suggested troubleshooting ideas. Unfortunately the main issue here seems to be finding someone with sufficient diagnostic experience to troubleshoot accurately.

 

[Dr Sheldon]

Unfortunately the main issue here seems to be finding someone with sufficient diagnostic experience to troubleshoot accurately.

Indeed !!


The only contact I have in the US is Paul Danner "ScannerDanner"

I learnt a lot from Paul !!

Shop Directory - SCANNERDANNER

Master automotive diagnostics with real-world training, step-by-step courses, and expert instruction. Don't be a parts changer. Join ScannerDanner Premium.

www.scannerdanner.com

 

[dn242]

@Dr Sheldon I was never able to get a straight answer from the shop about their diagnostic capabilities, so I ended up getting a cheap scope myself to do the RC test. (Note: I'm trying to get a trigger signal to identify the cylinders, but that requires removing a lot of parts on this engine to expose things like coils.)

There is definitely some variability between the 12 cylinders, but I'm not sure whether this is significant enough to indicate a compression problem. Do you have any thoughts or other tests that might help proceed further?

For some reason I can't post the image but here is a screen capture:
Raw data: https://postimg.cc/Wq74M9FB

Zoomed stable RC pattern: https://postimg.cc/NyGwWgnr

@EuroX The shop where I previously had the Flying Spur tried to do a leakdown test, but they couldn't do it because they were unable to crank the engine manually. I can't find anything in the Bentley manuals about leakdown / compression test procedures. Is there some trick or technique to crank the W12 for compression testing that you know of? They said it was impossible to get a wrench on the crank.