Rough Cold Start Idle. O2 Sensor ????

My 1996 VW Jetta GL 2.0 idles rough, puffs n putts when I first start it in the Morning. And if I let it sit long enough to cool down significantly it does it also. Once the car is warmed up and in use throughout the day it seems to start and idle fine. My fuel mileage is down around 15 Mpg. :frown: :shakehead And I am reading a few Oxygen Sensor codes too, Could this be a significant contributing factor? Any Ideas as to What could be my issue? :frown: THANKS !!

I had the exact same problem, and using my Robert Bentley service manual I hit it on one try. The sensor to replace (about $12) is on the coolant outlet flange on the cylinder head (attached to the top radiator hose). I forgot then name, but it has 4 terminals. My symptoms were the same...horrible cold starting (worse as temperature dropped here in Germany). A lot of flooding. This should be the first thing to try.

I see you stated you have some code reading. Would you please let us know what are the code numbers.
For VW Jetta, ther is too many things related to each others.

Thanks