I'm stumped and the stealership is useless

[Mitch567]

Help! I’m stumped and stealership is useless.
F15 X5 35d

I’m experiencing very rough idle/bucking and occasionally stalling. I'm relatively mechanically inclined to fix and troubleshoot, but this is my first BMW and my first diesel, so I have a lot of learning to do...

Bucking/stalling when...
-Ambient temp outside is 80f+
-The car is turned off and parked for 20min-1hr after coming up to operating temp, and then being restarted after heat soaking
-Only during the first few feet after selecting a gear (ie when reversing. Out of a parking spot and only when applying NO throttle)
-Especially noticed when below a 1/2 fuel tank
-Symptoms will disappear immediately after throttle is applied and doesn’t return until the car has sat again for 20min-1hr.

Previous owner didn't replace the Fuel filter in 45k. I replaced it thinking it was an easy place to start. No improvement.

Is this a fuel pump going bad? CBU? Dealership initially thought crank position sensor, but passed all tests. We're awaiting on BMW engineer's input apparently.

The weirdest thing in this whole ordeal is NO CODES! Nothing! I'm astonished that a modern vehicle (especially diesel) can stall while in gear and throw no codes.

Any help would be greatly appreciated.

Edit: Attempting to upload video of rough idle. Stay tuned.
Rough Idle:https://youtu.be/Mwtk0NRocK8
Bimmerlink Datalog of Car stalling immediately after startup: https://youtu.be/nDcDu9oteLE

[W37V]

Diesels don't like bad fuel and not replacing fuel filter would def cause bunch of issues.

I bet your fuel injectors are messed up (clogged). There might be some sediment in them. I would start there. I spoke to several mechanics who said that the fuel filter should be replaced more frequently than service manual indicates especially if you are buying fuel from stations where there is not much diesel traffic.

I had 3 bad injectors, but code showed only 1 being bad.

I would suggest they start there - replacing all 6 and doing software update.

[turboawd]

Does this also happen if you start and put in gear but don't move? Or only if you're moving?

[positiveions]

I read that sometimes even non-branded diesel can be dirty and may cause problem. Another problem I read is algae growing substantially in the fuel line causing stalling, rough idle, etc. Good luck on this buddy and update us.

[Mr.47]

Originally Posted by W37V

Diesels don't like bad fuel and not replacing fuel filter would def cause bunch of issues.

I bet your fuel injectors are messed up (clogged). There might be some sediment in them. I would start there. I spoke to several mechanics who said that the fuel filter should be replaced more frequently than service manual indicates especially if you are buying fuel from stations where there is not much diesel traffic.

I had 3 bad injectors, but code showed only 1 being bad.

I would suggest they start there - replacing all 6 and doing software update.

Any injector problems the car will throw pending code, and a MIL if the pending code is not resolved within a time frame or recurring frequently ista/d is good at looking at hidden malfunction codes.

To me it sound like air in the fuel line, must be sucking up air somewhere in rubber fuel lines (perhaps a cracked rubber fuel line), When you replace the fuel filter did you make sure you you have all the lines and the heating element installed properly? Did you forget any rubber gaskets for the heating element?

I'd look around all of the rubber fuel lines, from fuel tank, electric fuel pump, fuel filter and up to the high pressure pump, then proceed to inspecting the hard high pressure hoses and line for loose connections,

[Mitch567]

Originally Posted by turboawd

Does this also happen if you start and put in gear but don't move? Or only if you're moving?

Both.
It will happen while in park, neutral or drive. Stationary or moving.

[Mitch567]

Originally Posted by Mr.47

Any injector problems the car will throw pending code, and a MIL if the pending code is not resolved within a time frame or recurring frequently ista/d is good at looking at hidden malfunction codes.

To me it sound like air in the fuel line, must be sucking up air somewhere in rubber fuel lines (perhaps a cracked rubber fuel line), When you replace the fuel filter did you make sure you you have all the lines and the heating element installed properly? Did you forget any rubber gaskets for the heating element?

I'd look around all of the rubber fuel lines, from fuel tank, electric fuel pump, fuel filter and up to the high pressure pump, then proceed to inspecting the hard high pressure hoses and line for loose connections,

Thanks for the suggestion. I'll take a look at the fuel lines.
I doubt it's an issue with the fuel filter or gasket itself, as my symptoms occurred before and after changing of the filter.

Would air getting in the fuel system explain why my symptoms only occur when the engine (and ambient air) is hot?

[weareweird69]

Looking at the data-log. It looks like you lost fuel pressure... So, id say you've got a fuel issue. If you can find a way to put a pressure gauge on the actual system, POST lift pump, but before the High Pressure Pump, that'll tell you if the tank pump is bad.

[weareweird69]

Also, Algea in a tank is usually from sitting too long. OLD OLD diesel that sat somewhere, or organic material got inside the tank somehow.

Try to run the tank as low as possible, fill up from a good source, and add some algicide that you can buy from some retailers, I am not sure if the local parts stores carry it or not. That will rule out the bad fuel.

Ive seen water in diesel fuel a lot.... Not sure if these have a water separator or not, but do you remember getting water from the fuel filter when changing?