Problem with cold starting
 

I have a bora model 2004 1.4 16v with 75hp with petrol engine. The last two years it has one problem with the cold start. When the temperature on air is over 15 C it starts very well uploading to 1200rpm/h and after 5 minutes descends in normal position 850rpm/h. But when the temperature on air is down from 15 C it starts uploading to 950rpm/h and after 5-8 minutes descends in normal position (850rpm). I went to the vw dealership but they did not find the solution. Recently I replace the sensor for cold starting but the problem remains. Please help me. Thanks a lot.

If a dealer can't find a solution that's strange.

You need to find someone with VAG-COM\VCDS to investigate?