Hi,

No, nothing is broken, at least I am convinced it is not, just the idling behaviour of my t-jet got me curious:

1. When the weather is cold (up to 4 deg C or so) and the car is really cold in the morning - when I start it up it goes up to 1000 rpm, not one rpm more and stays there for a while, and then drops to 850 when warm enough. (Assume we are not driving anywhere). And everything shows me this is the intended behaviour - switching on and off various electrical receivers keeps the rpm at 1000.

2. When the weather is warmer (8 deg and up), or when the car had not enough time to completely cool down - when I start it up it goes directly up to ~1500 rpm. And stays there again for long enough to warm the engine up a bit and then drops directly to 850 rpm, without keeping intermediate idle rpms, just goes in short steps all the way to 850. Same here - it seems like it wants it to be this way.

This does not bother me, the car works and there are no problems. I just do not see the rationale behind this. Is it assumed that it is safer not to rev the engine up when it is very cold, or what? Or is it the torque reserve strategies and things like that in the ECU that just try to get the engine warm as fast as possible and this is the effect?

I have exactly same thing but I assumed it was because I'm running atmospheric dump not recirc.... I try to use cold start protective oil

Mine does the same as yours in cold weather as it is supposed to but when warmer it just goes straight to 850rpm. 1500 is not right, aspart from anything it would burn too much fuel and push up the official co2 figure on the urban cycle.

Mine is exactly the same mate I've often wondered why it does it!

May be there is a sensor issue...

I do not think it is a sensor issue. Judging from all the documents I have read about Bosch ECU's this is very likely part of some very involved strategy to (a) prolong the engine life, (b) save the environment, and (c) make the engine warm up as quickly as possible.

Makes sense I suppose but it just seems wrong... It's just I thought you should allow the engine to warm on its own? Maybe I'm wrong but I have treated my engines this way and they have all out lived there shell's....

Yes, it should warm by itself, but when you load it without increasing the rpms it will happen quicker. You can do this by switching on the receivers, but also by playing with the ignition advance, that is, inducing load by reducing spark advance.

But I am theoretising here, these ECUs are a bit too complex for me...