Random stalling at lower speeds - Surging at higher speeds

[Ricky Bobby]

Two random issues going on and wanted to document in case someone comes across -



Bone stock 82k miles 2013 X5D -



This one is actually scary enough to my wife that the car randomly stalls/shuts down while driving and its usually coming off of a stop or at lower speeds - happened once on the road today and once in a parking lot and then once as well by our mailbox - she is going to park the car for now -


I drove it this morning and around 50mph in 5th gear the car surged as if it was skipping a beat -


Hooked up to ProTool and only codes showing are in the DME:
3E90 - Crankshaft sensor, signal
48DC: Boost pressure sensor, plausibility


I am assuming the crankshaft sensor is going and showing me symptoms but wanted to be more assured before I order one - I have a long list of maintenance items to address in the coming weeks.


I know the crankshaft sensor is at the back of the engine and I believe the starter has to come out which sucks.


I don't know how to check or where the 'boost pressure sensor' is - although with the plausibility code I really don't know if thats the issue.


Been a long time guys but with a 2 year old now its imperative we keep the wife's car running great.

[andrewwynn]

My first repair six years ago on my e53 was nearly identical symptoms caused by faulty cam sensor.

Crank sensor failing will cause the same. It's lucky if you get an actual code usually you have to sleuth out from symptoms.

I've never seen a case where you get a code for cam/crank sensor and that part isn't worn out.

That part is "mission critical" as in the engine won't even start much less run without it. It's stupid precise as in the computer is estimating how many tenths of a millisecond before three next pulse to determine if the next power stroke delivered. If it's late even a handful of tenths it knows there was a misfire.

Anyhow it needs a new crank sensor get only OEM or you will likely have symptoms with no error code related to the part.

[andrewwynn]

The sensor will soft fail. I drove my car clearing any codes that came up for a month before finally finding the suggestion on xo it was related to the cam sensor. You can clear codes and drive to set if the pressure error comes back on its own. There is a specific defect related to that error that is not the sensor but tied to the blow off valve i believe. (eg doesn't open far/fast enough and pressure gets to an "implausible" level.

[Ricky Bobby]

I agree and after more research I purchased a new cam sensor (top of engine) and crank sensor (back of engine) -



Crank sensor I ordered the "OE", Bosch - They make the genuine sensor I just couldnt pay $80 more for it -


https://www.fcpeuro.com/products/bmw...sor-0281002477


Cam sensor I also ordered the OE which is a German made VNE sensor - I agree with not straying from Genuine or actual OE brand for sensors as precise as these -


Will report back but I also spoke to TuneMyEuro (AARodriguez Corp) and once I gave him the symptoms and codes he said its a very common issue and get the crank sensor replaced because when it fails completely car will not restart (he sells the Bosch crank sensor and VNE cam sensor as well says they are good to go as they are the original equipment)



https://www.fcpeuro.com/products/bmw...or-13627792256


In regards to the boost pressure sensor code I wanted to clear my bases so I ordered a MAP sensor which just presses into a grommet in the manifold and very commonly gets gunked up, although I think that is a secondary preventative item, it will not cause the car dying like the crank sensor will.

[andrewwynn]

Does diesel have only one cam sensor? I've only replaced the intake cam sensor on my m54 about 70,000 miles ago. The exhaust sensor still working at just shy of 200,000. I'll prob order a replacement on my next FCP order.

[Ricky Bobby]

Cam sensor on top of the engine by oil fill cap and crankshaft sensor (the one I believe is failing on mine) is under the manifold and above the starter


The X5 is going in next week for manifold removal anyway and a plethora of other work so its going to get crankshaft replacement sensor at that time as well - and then we should be able to put this to bed -

[andrewwynn]

Good plan on the sensors

[Ricky Bobby]

It was the crankshaft position sensor above the flywheel at back of engine -

I happily paid the $160 in labor to R&R the sensor as the starter had to come out and its almost a blind job - she's good to go now (and even better after some other performance and maintenance items)

[andrewwynn]

That's great resolution! So happy to hear such a low mileage copy get back to life! I don't feel bad that my second guess turned out to be the culprit.

[getty150]

Man glad you guys came to a solution...the crankshaft position sensor! I have the 04 X3. Yesterday I went after the cam position sensor...no stalls yet. But I'm inclined to go with the crankshaft position sensor....hidden under my starter. Hince a starter job. I can do it in a day. And I got a couple days off before going back to work! Well, again glad I ran across this thread, thanks guys for being thorough!
Cheers!
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