[Shrocat]

Your car will run rich with it disconnected, which will lead to increased emissions, decreased fuel mileage, and ultimately lead to the untimely demise of your catalytic converter. Now, other than unplugging it what made you think it was bad? Did your check engine light come on? If so, did you read the codes?
If you do not have a code pointing to the sensor, I would be more inclinded to suspect a faulty temperature sensor, telling the computer that the engine is warmer than it really is. On the old carburated carbs the choke made the fuel mixture richer until the car warmed up. On the modern computer controlled cars the computer gets the temperture from a sensor, and if the sensor says the temp is cold it makes the fuel richer. If the sensor tells the comp that the engine is warm, while it is still cold, the fuel mix is too lean. Which leads to hard starting, rough idle while cold, and stalling when putting in gear.