2.0 TDI engine runs poorly at low RPM when cold

Hello,
It's about my annoying Audi B7 2.0 BRD (the notorious 170 hp engine) again.
Besides the fact that it still smokes and smells (which is probably due to the particulate filter or its seals), I mainly have another problem in the winter: when it's cold, it runs terribly. It's like a 50 horsepower gasoline engine where the cold start regulator isn't working. I've never had a diesel stall so often. Even if you can hear it struggling and immediately press the clutch, it still stalls. Once it's warm after about 5 minutes, it runs quite well. This problem is noticeable down to an outside temperature of around 10°C. It starts cold, but still quite well (not quite as perfectly as my old 1.9 TDI (90 hp)), but always within one to two seconds.

My initial assumption is that he doesn't realize the engine is still cold. So, with an outside temperature of 5°C after a cold night, I read all the engine-related temperatures. They were between 4 and 7°C. So, the sensors should be working fine.
The temperature reading in the particulate filter is 17°, but this is likely due to the wide measurement range, and it certainly won't be used by the engine control unit.
When it's warm, it runs really well, although I expected a bit more for 170 horsepower (which might be subjective). It even pulls cleanly from 1000 RPM in a low gear, with very responsive and elastic behavior. This engine has a bad reputation due to technical flaws, but when it's in good condition, it really runs great.
"The only problem is the cold start, which is a disaster. I don't see the PDE issues mentioned above as the cause of this." Especially when it's cold, it barely smells, and it doesn't show any smoke at the traffic lights; that only becomes noticeable when it's warm.
MGS software has update version 9973, which, as far as I know, should be the last one, and it likely includes optimizations for the cold start process (I think I read that somewhere).

Oh yeah, I've also cleaned the EGR valve and the throttle body before. But it didn't change anything. Does anything get stuck when it's cold?
Does anyone have a suggestion for what other data I should log to help track this down? My second BRD, with new PDEs, also exhibits this issue, but it seems less pronounced (although I haven't driven it much in the winter, and it's now deregistered). I suspect this effect is more common, and that someone here has already solved it (I've been searching for a long time, but haven't found anything).

Thank you and best regards.

Andreas.

Hi Andreas,
Are the spark plugs okay? They don't just run before the start.
but also for a while after that.

Best regards,
Micha

Hello, thank you for the tip.
At least no error code is being stored for the candles. Many also claim that they only glow until the start, which is what I've thought so far. However, I'm happy to be corrected by newer findings. In the past, we were also taught that a diesel engine doesn't have a lambda sensor. It was true then, too.
Could it be that weak (but not completely burned out) glow plugs have such a significant impact on cold starting? Has anyone here had any specific experiences with this engine type?

Regards,

Andreas.

All of my defective CNC machines had an error entry. For the 1.9 Touran.

Hello again.
I think I'll go ahead and replace the glow plugs, although I'm not really convinced they're the cause. But they're definitely old. Unfortunately, everything seems to cost twice as much on this awful engine (BRD), even the glow plugs. Twice as much as on my 2.5 TDI. And the tiny rubber rings (seals) for the PDE injectors cost almost three times as much as for the 140 HP version (a set of 4 original Bosch rings starts at €29, while a set of 4 for Siemens PDE injectors doesn't go below €80). Of course, there's a huge price difference for the PDEs. "I wish I had just gone with an older model with a distribution pump..."
Regarding the topic above: Does anyone have any suggestions on what data would be useful to log during the initial startup phase?

Regards,

Andreas.