Scotty, I have a 2013 audi a4 with 200,000km. for the past few months when I start the car after sitting overnight in below zero weather, the car idles over 1000rpms. when the idle gets down the engine of the car shakes and feels like someones kicking it. I also bought a OBD2 scan tool and the only fault that showed was the purge flow. All my maintenance is up to date but can't find the solution to my problem please help !!!
Sounds like if the engine is revving up, you may have a bit of a vacuum leak... However, if it is only doing it in the cold I wouldn't worry about it.
If the engine is shaking and there are no misfire codes, I would check the motor mounts.
A lot of different things cause rough running engines.
Check out this video as well:
https://www.youtube.com/watch?v=1kb-9qLu00Q&ab_channel=ScottyKilmer
Another thing to keep in mind is internal engine wear will also lead to a rough idle at startup. If your engine has severe wear, changing the spark plugs isn't going to help much.