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Just an update - got the car back after another couple days at the dealership. Here's my cross post from the 1 series board
I look at the service invoice (all no charge thankfully under factory warranty) and their troubleshooting for the rough idle was pretty damn impressive. Here's all the steps they performed (after each step, the invoice documents "No change"):
1. Updated vehicle software.
2. Swapped 6 new ignition coils
3. Inspected spark plugs
4. Replaced eccentric shaft sensor
5. Smoke tested intake for leaks
6. Checked vanos function
7. Checked fuel pressure
8. Tested sample of gasoline and found no water/contaminants
9. Performed ethanol test and found 5% (????)
10. Filled injection flush container with fresh gas and ran through fuel rail
11. Installed 6 new spark plugs
12. Swapped injectors from known good car
13. Checked crankcase ventilation pressure
14. Increased idle speed
15. Performed compression and leakdown test (all cyl within range and good psi and within spec, good to know!)
16. Compared dme status requests to known good car
17. Unplugged MAF sensor
18. Checked cam timing
19. Swapped pre cat 02 sensors from known good car
20. Submitted PUMA case to BMWNA and instructed to try swapping post cat o2 sensors
21. Instructed to replace eccentric shaft.
22. Vehicle operating as designed at this time.
Here's what I learned - South Bay BMW (right down the street from me) has some competent mechanics in that if I were trying to diagnose a rough idle, I wouldve done everything they did. They threw the book at the problem, and if it weren't for BMWNA somehow knowing to check the eccentric shaft itself, I don't know if the problem would've ever been fixed.
Why I'm sharing this with everyone is in the hopes that in the future, if someone else has a rough idle, you now know the 21 different work steps that BMW mechanics perform to try and diagnose the exact problem. Hopefully you don't end up all the way down at #21 because the cost of the eccentric shaft itself is some $600. I don't even want to know how much the labor cost is to replace it. FYI - the sensor itself is also $360. Too bad they didn't leave in the new spark plugs, coil packs, o2 sensors, and injectors. That would've been a nice bonus.
The car is no longer under full warranty, but I still have extended maintenance and CPO. This would've been covered under CPO (I think) but I shudder thinking about what recourse I would've had had the car not been under warranty.
Hope this thread will help someone in the future who has the same symptoms.
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