When I had a crack in my intercooler the idle was very erratic at startup.

 

MAF sensor issue( clean it or replaced it). unplug it , and start the car , see if its idling bad.

 

did u guys figure out what the exact problem is? I too have a similar issue with my A4 1.8T!

 

I have an 2007 Audi A4 with 103k and was having the same issues. Rough idle, lack of power and sometimes plumes of smoke coming out of the exhaust with hard acceleration. I did some research and just got done replacing the PCV valve and oil change with Mobil 1 0W-40 oil and instantly I saw a huge difference. Starts up great and runs so much smoother. It has also increased my fuel efficiency. I am still getting a very small vibration at first idle and need to look into it, but I probably need to realize that its because it has 103k. I also just got done replacing my motor mounts. It is a very common thing for Audi's to have these go bad. There are two mounts on either side of the engine. These mounts look like canisters and are filled with a liquid gel pack, which absorbs and transfers the natural shaking of the engine and after awhile of use they will bust and leak. When this happens your car will start to absorb that shaking of the engine therefor giving it, what seems like, a rough idle. Good Luck if you haven't already found the issue.

 

Were your mounts leaking? I had one spring a leak and had it replaced--the other seems fine still (78k miles).

 

I saw the puddle after the mount leaked and it was a reddish orangish color. It took it in right away and they told me the mount under the turbo had fully leaked. There is only so much they can leak. When I took it too fix it they replaced both even thought he other one was fine. I am not sure if that is standard procedure.

 

You don't have to replace both, but it probably didn't hurt. Just cost a bit more, but now they should last for a while.

Interesting. Mine leaked purple and it was not leaving a puddle--just weeping down the mount and staining it.