Update in my scenario,
Cold temperatures, cranking, but no ignition.
After few days/week of long cranking in the cold have drained a car battery a bit, after cranking few times the voltage also dropped to 11.6V - that is called a totally exhausted battery and needed a proper recharge - which i did for 24 hours - now it shows 12.6V.
After your thread read I inspected a Knock sensor, I wiggled the wiring and the ignition process improved I think that it might be a merely broken wire somewhere in the way to connector B21. For now I locked wires in "superposition" and engine starts normally on cold mornings and idling also improved.
Sometimes while driving and then I push on the pedal I get some jerking I think this is interconnected with knock sensors readings, (firstly I suspected the coil packs or a spark plugs).
And rarely but sometimes after turning off the engine, and on restarting the engine - cranking, but NO start. Reconnecting the main B21 harness always helped to be able to start the engine, but acceleration hesitation remained.
Planning of removing the whole wiring harness from the engine (B21 harness part) and doing a detailed wire inspection.
Also will clean the ground connector points.
