My Audi A6 18t is misfiring and smoking - 2001 Audi A6

You didn't say what colour the smoke is. I assume it is from the exhaust and is darkgrey/black sooty sort of smoke which along with the engine misfire would indicate faulty diesel injector(s).

Typically bad rings, burning oil... when warms, metal expands, and seals better... check pcv system first, its cheaper, but generally will smoke at all times when bad... valve stem oil seals another posibility

It could also be an ignition sensor, mine went out and the car kept misfiring. Once I had it replaced that took care of the misfiring issue.

Audi, European design, parts may be hard to find for this, I suspect the automatic choke assembly is faulty, hence giving you the wrong combination of air and fuel mixture causing the smoke. You could however, if you are willing, to remove the assembly and try lubricating and cleaning it, as it may have carbon build up blocking the channels inside. Hope it works, Good luck

first check your glow plugs that they are not faulty,if faulty replace them,then get a bottle of injector cleaner and put it in your fuel take and replace your diesel filter,and also change your oil and oil filter,maybe your hydralic lifters are not preasurising when cold

check output voltage of altenator if its above 15volts change it

If your engine is not misfiring but it vibrates too much while idling your motor mounts might be getting worn out. I had a Nissan with bad motor mounts. I was ok in park but when you put it in gear it vibrated a lot. It smoothed right out as soon as you started moving.

replace the speed idle sensor

fuel injectors?, fuel pressure? low compression? even vacum leaks can cause misfires,

IF YOUR CAR IS GIVING YOU A P2181 CODE YOU HAVE TO  A: USE A SCANNER THAT HAS ALL SIXTEEN PINS LIKE  A SNAP ON SCANNER  B: TAKE IT TO A REPAIR FACILITY