How will a car act if the oxygen sensor is bad?

Answer 1

I am not a mechanic but I know just enough from personal experience to say this much: I own a 1992 Volkswagen Jetta GL (gasoline). When the oxygen sensor goes bad on this car, the results are predicatable and consistent: it is always hard to start after sitting parked overnight or for several hours (say 8 hours). Instead of taking approximately 2 seconds to start the engine, it would now require approximately 8 to 10 seconds (up to 15 seconds) to start the engine. It is also my understanding that a bad oxygen sensor will also contribute to the destruction of the catalytic converter, requiring replacement of that part. What if the oxygen sensor is manually disconnected? Yes, this can be done. The results on my car is gas mileage is reduced from a peak of 33 mpg (highway/city) to about 28 or 29 mpg (ditto). The performance of the car is not affected but there is a noticeable but slight odor of fuel or oil when it is running cold. A disconnected oxygen sensor immediately resolves the hard starting problem (assuming all other parts are functioning to spec). Beyond that, I could not advise you on what would be, if any, the long term performance consequences of running around with a disconnecteed oxygen sensor. This is only my experience and only with this type of car.