1998 Audi A4 O2 sensors

My 1998 Audi A4 has 125k miles. The check engine light recently came on, and the shop told me that 2 of the oxygen sensors are running slow. My car has a few problems already (ABS module broken, cruise control broken, radio antenna broken, needs two new tires, exhaust hanger broken, AC compressor is gone, and it will need a new clutch soon) and I am a poor student, so I don’t want to throw my money into a hole. My mechanic told me that I either need to make a commitment or divorce the car. I only need this car to last me another few months. What will happen if the O2 sensors continue to run slow? Is this dangerous? Will I have warning before the car suddenly won’t move anymore? Should I toss the car now, or will it last a little longer? Please help. Thanks!

Not sure what “run slow” means. How many more months is “another few?” What happens after you don’t need this car anymore?

You should replace the O2 sensors if that is causing the CEL to stay on. Otherwise you won’t know if something else happens and trips the warning light. But maybe at this point in time you don’t really care. Hopefully the clutch will last. If not, then I would say it would be time to part ways. I would also try to get some good used tires to replace the bad ones just for safety reasons.

I’ll be moving to NYC in August, so I won’t need a car there. At that point, I’ll either sell this car or donate it to a high school/trade school.

The mechanic turned off the check engine light and it hasn’t come back on since then (a few weeks ago). Hopefully the tires and clutch will last until August.

The mechanic said the catalytic converter will break if I don’t replace the sensors. Is this true? What will happen if the catalytic converter goes while I’m driving?

If you limit your driving you may be able to stretch this out until August. There are many who ignore their Check Engine Lights for years at a time. Be aware, however, if the car needs PA inspection it will not pass with the CEL on.

I don’t think this, by itself, will cause the car to quit running all of a sudden.

The combined weight of neglected repair and maintenance, however, might.

The catalytic converter won’t “break.” It just becomes less and less efficient at cleaning the exhaust of pollutants and your gas mileage will probably be reduced. If the light is off just keep driving.

With your fingers crossed.

If the fuel injection computer gets faulty data from a slow O2 sensor, it will not be able to hold the correct Fuel/Air ratio well. At times the F/A ratio will be too lean and you will get missing and stumbling. At other time the F/A ratio will be too rich and the extra fuel will be burnt in the catalytic converter causing excess heat in the converter. Its like the slow reaction time of a drunk drive on the highway – can’t keep the car between the lines.

As previously said the Check Engine Light could come back on. You would not be able to pass emissions inspection with the CEL ‘on’. The catalytic converter could overheat and melt internally causing loss of power. Don’t worry, most of the problems are not catastrophic and usually just get progressively worse. Not dangerous IMHO.

Hope that helps.