Diagnosing Hesitating/Misfiring X35i with No Codes

[ClutchKickChris]

Our 2012 X5 has always ran great, I do all maintenance myself (oil changes every 7500 miles or earlier, plugs, coils, diffs flushed, trans flush and filter, oil filter housing gaskets, air filter etc etc.). Early last year, since COVID, it barely got driven as much. It currently has 111K miles. All of a sudden it's like a bomb went off and this past year I am having 2 serious issues with the car pop up, they are:

• Stutters and misfires at partial load
• Waterpump runs with engine off when the car "wakes up" (unlock it, open a door, it detects comfort access key is close)

Its been stuttering/misfiring at partial load (normal acceleration) between 1500-3000 RPMs. I immediately thought it was bad gas since it was filled up at a no-name station once and it started shortly after, the next time we filled up I made sure to go to our regular shell gas station and put 93 in it. This seemed to fix it on the first test drive, but the next day the stuttering returned.

So I tried to purposely drive it in this stuttering/misfiring range to get a CEL, this never happened even after weeks of driving.

One interesting fact is when the car is floored WOT it has zero issues and runs perfect, it's just in the light load (normal acceleration) range.

I then suspected the coils/plugs but all 6 were replaced within 1.5yrs (Bremi coils) from FCP euro. I noticed 1 coil looked a bit different on cylinder 3, it had a white top instead of black. I got a new black top Bremi coil to match the rest but that didn't fix it either. Without a CEL its very hard to diagnose this further.

I also pulled the spark plugs to inspect them and they looked good and were gapped correctly.

With my scan tool (Deep OBD) I drove the car in the stuttering range and monitored the 6 cylinders for misfiring (I think it was called knock adaptation?). What I observed is that ALL cylinders randomly showed misfires.

After doing a lot of googling it seemed that the likely cause would be carbon buildup on the intake valves. So I had the valves cleaned (they were shockingly dirty with thick buildup of black sludge in all intake ports), and just test drove it last night but the stuttering is still there!

Another issue popped up during this timeframe where there's a DTC for waterpump, alternator, oil level and battery sensor communication failure. From googling I suspect that the waterpump electrical connector is leaking coolant internally into the connector, and shorting out its power to the CANbus data connection (there's threads on this defect on recent replacement waterpumps doing this), thus killing CANbus data for it and other devices on that bus. Could this be related to and/or the cause of the stuttering/misfiring?

I've been chipping away at this issue for a couple months now and not getting anywhere. Next on the list is replacing the waterpump (FCP Euro warranty).


List of current codes:

DME/DDE (Engine electronics):
Error code: 3847
LIN / BSD, message; alternator: Missing, Fault not currently present, no matching perceived symptom, Fault does not activate warning light
Environmental conditions:
- Frequency: 9
- Logistic counter: 40
- Kilometer reading: 179576 km | 179792 km | 179944 km
- Identification, alternator, manufacturer: 255 - | 255 - | 2 -
- Timer since starting (16-bit): 218.7 s | 15 s | 248.9 s
- Current status of alternator: 14726 - | 14470 - | 14470 -
- El. machine terminal voltage: 1.44 V | 1.43 V | 1.55 V

DME/DDE (Engine electronics):
Error code: 38A4
BSD, message; intelligent battery sensor (IBS): Missing, Fault currently present, no matching perceived symptom, Fault does not activate warning light
Environmental conditions:
- Frequency: 12
- SAE fault code: P150A
- Logistic counter: 40
- Kilometer reading: 179576 km | 179792 km | 180040 km
- Engine speed: 1440 1/min | 0 1/min | 0 1/min
- Battery current from IBS: 1110.7 A | 1110.7 A | 1110.7 A
- Batt voltage from IBS: 65.54 V | 65.54 V | 65.54 V
- Battery voltage: 13.56 V | 12.62 V | 12.62 V

DME/DDE (Engine electronics):
Error code: 378F
BSD, message; electric coolant pump: Missing, Fault currently present, no matching perceived symptom, Fault does not activate warning light
Environmental conditions:
- Frequency: 9
- Logistic counter: 40
- Kilometer reading: 179576 km | 179792 km | 179944 km
- Engine speed: 880 1/min | 1120 1/min | 1320 1/min
- Engine temperature, linearized and converted: 84 °C | 35.25 °C | 72.75 °C
- Recommended current RPM of BSS coolant pump: 255 1/min | 255 1/min | 255 1/min
- Battery voltage: 13.56 V | 13.56 V | 13.75 V

DME/DDE (Engine electronics):
Error code: 3446
BSD, message; oil condition sensor: Missing, Fault currently present, no matching perceived symptom, Fault does not activate warning light
Environmental conditions:
- Frequency: 9
- SAE fault code: P1521
- Logistic counter: 40
- Kilometer reading: 179576 km | 179792 km | 179944 km
- Engine speed: 880 1/min | 1120 1/min | 1280 1/min
- Control unit internal temperature: 42.75 °C | 23.25 °C | 28.5 °C
- current battery voltage: 14 V | 14 V | 14.8 V
- Time after end of starting: 263.79 s | 59.32 s | 263 s

DME/DDE (Engine electronics):
Error code: 3163
Fuel tank ventilation system, shutoff valve: clamped open, Fault currently present, no matching perceived symptom, Fault can activate a warning light (emission warning light or engine warning symbol)
Environmental conditions:
- Frequency: 2
- SAE fault code: P149D
- Logistic counter: 40
- Kilometer reading: 179688 km | 179872 km
- Engine speed: 1400 1/min | 1520 1/min
- Fluid level in fuel tank: 14 l | 69 l
- Filtered factor, tank-venting adaptation: 1.5 - | 0.5 -
- current battery voltage: 14 V | 14.35 V

DME/DDE (Engine electronics):
Error code: 387F
Power management: Standby current violation, Fault not currently present, no matching perceived symptom, Fault does not activate warning light
Environmental conditions:
- Frequency: 2
- SAE fault code: P160F
- Logistic counter: 39
- Kilometer reading: 179784 km | 180040 km
- Time during which standby current is 80..200 mA: 14.93 min | 14.93 min
- Time during which standby current is 200..1000 mA: 836.27 min | 59.73 min
- Time during which standby current is above 1000 mA: 731.73 min | 44.8 min
- Cutout time: 50 s | 50423 s

JBBF (Junction Box electronics):
Error code: A6CF
JBE: AUC sensor, Fault currently not present, Fault, sensor
Environmental conditions:
- Frequency: 1
- Logistics counter: 31
- Mileage/km reading: 179904 km
- Vehicle speed: 8.5 km/h
- Battery voltage: 13.76 V

PDC (Park Distance Control):
Error code: AB48
REAR VIEW not available, Fault currently not present
Environmental conditions:
- Frequency: 4
- Mileage/km reading: 179664 km
- Ambient temperature: 16 °C
- Battery voltage: 13.81 V

STVR/TEBF (allround-view camera):
Error code: AB74
Rear view camera not aligned, Fault currently not present
Environmental conditions:
- Frequency: -1
- Logistics counter: -1
- Mileage/km reading: 179664 km