BMW Repair: 2000 BMW 323i shakes on cold idle, vacuum leaks, vent valve

Question
Hi,
I bought a 2000 323i recently from a dealer. After almost 2 weeks, when I start the car, it shakes pretty badly on cold idle. It goes away after I drive 3 or 4 miles. Can you please help me with this? Thanks a lot!

Answer
Hello Ravi,
It can be due to any of a number of possibilities. But all or most of them are related to emissions. Don't you have a warranty from the dealer you bought it from? If it was from a BMW dealer, I am sure you have CPO warranty. Then you can have it diagnosed and repaired there. If not, then you have to do it the hard way.
Do you mean that after driving 3 or 4 miles, the idling is already smooth? Or is it simply slightly smoother but still rough?
First, eliminate the possibility that you have wornout or fouled up plugs by replacing your spark plugs. While replacing the plugs, you can also see if there is oil outside the plugs meaning the valve cover is leaking oil. If there is oil inside the plugs, either you have a bad crankcase vent valve or bad piston rings.
If after replacing the plugs, it is still idling rough on cold starts, there is a high probability that the idle air valve is bad (but idling should still be a little rough even when hot). The injectors might also be going bad. Or there could be vacuum leaks. I could go on and on and on with so many possibilities.
The best way is for you to bring it to a BMW  dealer and have it diagnosed with a scanner and pay the minimum one hour diagnostic fee. Then look at your options after their scan and diagnosis. Pay special attention to adaptation values (fuel trim in non-bmw language).You don't have to have repairs done by the dealer. You could just use their scan and findings and maybe have the repair done by somebody else or by yourself.
I hope I had been of help.
Tino