I have a 2002 A4 1.8T Quattro that has a cold start issue. When I start the car in the morning it starts real rough, misfires for about the first 10 seconds, then smoothes out and runs fine. After that the car will warm start fine for the rest of the day, but the next morning has the same issue.
Codes that come up:
P0420 - catalyst efficiency
and random cylinder misfire codes

Any ideas would be great, I've read about O2 sensor heater being bad, causing poor readings until it heats up.

 

New coilpacks or ICU would be a good start, or maybe its your cat. Not really sure, start with the keep stuff, when your driving do u see you cat getting really hot, like red hot. Then you have a bad cat. But i would go with easy/cheaper stuff get a new coil pack and switch it out and see if it keep ropugh idling.

 

Do a search on coolant temp sensor. It seams like that is what you are describing, but I admit, I have no idea what the code means.