E93, N54 - Cold Morning Start Idle - Looking for Input

[Codes2]

Hi Friends,

You helped me with my (new to me) E92 a few months ago, which resulted in Plugs, Ignition Coils and a VANOS solenoid. Thanks.

That car is gone and I'm in a (new to me) E93, N54.
No codes show or are stored using the OBDII or JB4 reader.
When starting the car at around -10 Celsius (14F) it catches instantly, no stumble... but then the RPM drops after about 10 seconds to around 700~ and it runs really rough.
I tend to sit in the car, holding the idle around 1000-1200 for 60-90 seconds - after which letting the idle drop it's OK. (totally OK)

My take on things:
- I don't suspect Ignition Coils, as a misfire feels more dramatic to me (though usually I experience them under acceleration).
- I'm somewhat suspect of the RPM lowering too quickly after starting before it warms... maybe the choke is changing to quickly?
- I doubt Injectors also, as that should feel like an Ignition Coil (or if sitting over night with Pre-v11 Injectors, it should take longer to start).

If it's RPM dropping or Choke changing too early - I have no idea how to quantify or qualify this. (it's my 20 years-ago car knowledge making me think this is possible... but it's not been an issue for me for many moons on Fuel Injected cars)

Maybe the simply need time to get hot... which could suggest an over-gap or dirty?


Thoughts are most welcome!

Thanks,

[Codes2]

I've noticed that if I drive away before the 90 seconds are up, I'm liable to have a cylinder misfire and it cuts fuel until I restart.

I still think it drops the revs too soon, but that shouldn't result in a cylinder shut down imo unless there is plug, injector or coil issue.
Odd is that I've only seen this symptom on -10C to -27C days.
No issue if i let it warm slightly first.

Insights and opinions welcome.
Will work on pulling codes next time.

[RocketSurgeon]

Definitely start with codes. Is it the same cylinder that cuts out, or different ones?
Raising the idle speed with ISTA+ helps some. The idle speed is set a smidge too low from the factory for efficiency, bumping it up by 50-80rpm helps considerably.

[Codes2]

Thanks RS.
I'm better equipped to catch codes quickly now.
Does ISTA allow for extending the raised idle on startup?

[RocketSurgeon]

I think ISTA just allows you to set base idle. There are other coding changes that can change idle behavior, but I haven't explored those. ISTA+ or MHD are the easy ways to adjust idle

[Codes2]

Thanks.
I will possible raise the base idle the small amount as indicated, though less for this 'winter stumble', and more for general reasons.

Note: Loving my JB4, well beyond just boosting. Nice code capturing, etc. Would be nice if there was a 'Copy' button though.

Codes
29CE Misfirings, cylinder 2
29CF ", cyl 3
29CD ", cyl 1
29CC Misfirings, several cylinders

Interesting it was a 'bank'.
This couldn't indicate VANOS, could it?
I know there are two Solenoids, but I think they are Upper/Lower, not Bank 1/2. (open to being fed valid intel... learning)
I understand that each bank drives a Turbo, but I'd expect different codes if one was still waking up.

My enterpertation
So, 3 Cyl, 1 Bank... not Injector, not Spark, not Coil...
Dirty Intake Valves? (no idea on history of Walnut blasting. car has 175,000KM. feels sweet when warm though)
Or something (dreaded) VANOS related?
(note - only on very cold start ups, if I pull away light-to-medium-light acceleration before 90 seconds)

Thanks!

[RocketSurgeon]

I don't think it's VANOS or turbo. Both turbos feed into the intercooler, so all six cylinders receive the same boost. The 2 VANOS solenoids are for intake and exhaust, they work all 6 cylinders simultaneously. Check that all your wires and grounds are tight. Carbon caked intake valves are a very real possibility. A clogged precat is a very remote possibility, though that affects each bank individually. If you have early injectors, they might be suspect. They contain a thermal-compensating oil that might not like the cold. A bottle of Techron fuel system cleaner twice a year is a very good idea. The injector tips sit in the cylinder, so they can get quite dirty.
Quick note on the VANOS and turbos. Both are heavily dependent on oil. Running a good 5w-40 synthetic like Motul or T6 will make sure you get lots of life out of them. I would go no more than 7000k miles on an oil change.

[Codes2]

I received the identical codes again this morning. (i like consistency)

Thanks for that info. I'll try to read up on the VANOS more soon.
I change my oil approx every 5000-7000 KM at the dealer. (same cost here)
I'll run a cleaner tonight.

I may look into getting the walnut blasting done shortly if this morning stumble persists.