When to replace O2 sensor?

[CT Mike]

What are the symptoms you experience that tell you it's time to install a new 02 sensor? Thanks, Mike

[Bob Kontak]

Hi Mike, see post #4.

Another Idle hunting 89 Carrera


If you have a multi meter, I would tap a wire into the O2 connector and read the voltage as the car is idling after warm up. The sensor does it's voltage thing all within one volt. While running, the voltage should change within the one volt range as it sniffs rich and this higher voltage sends a signal to the brain to lean it out. Then it sniffs lean and sends a lower voltage richen-up signal. On my 81 SC it only takes a couple of seconds to switch between the two states and you can hear the motor change pitch. The Motronic system is more sophisticated and I don't know if you can hear the idle pitch change on a 3.2. Pitch is different than RPM.