checking mixture via O2 sensor voltage output?

Jared at Pelican Parts · 09-14-2005, 03:13 PM

I'm thinking that my car is running a bit lean and I was thinking that since the O2 sensor generates a voltage based on the mixture, Cant I use that to richen up the mixture once the car is fully warmed up?

What im wondering is what should the output voltage of the sensor be when it's close to being dead on?

Jeff Alton · 09-14-2005, 03:23 PM

It should be between .2 and .8 volts.

Jeff

ausgezeichnet · ausgezeichnet's Garage

I used the numbers Jeff posted and got it pretty close. In fact it cured an idle hunting problem.

911Mac · 09-14-2005, 08:10 PM

Try this link for a graph showing both narrow band and wide band o2 sensor voltages.

http://www.msefi.com/msinfo/manual/mwire.htm#ego

You'll have to page down to the graph titled "Oxygen sensor output - Narrow and wide band". Be sure to read the paragraph just to the right of the graph called "The wide Band Advantage". They point out that the narrow band sensors are basically not very accurate, only telling you if you're rich or lean.

If you're running the factory o2 sensor you have a narrow band sensor.

If you upgrade to a wide band o2 sensor, most provide a narrow band output that can be fed into your existing ECU and a gauge that will display the A/F ratio the wide band sensor is seeing. Our host sells the Innovate model.

-Mac

ChrisBennet · ChrisBennet's Garage

Basically, the narrow band O2 sensor has 2 "states": too rich or too lean.
You can tune the mixture to some extent by getting the duty cycle close to 50/50 i.e. half the time at "too lean" and half the time at "too rich". Never tried it myself though.
-Chris

targa80 · targa80's Garage

I have used a 6 cylinder dwell meter to actually get a visual indication of the sensor output to the Lambda control box. When the needle is hunting over a wide range it is compensating for either rich or lean condition. I was able to adjust the mixture so the needle movement was at a minimum. After the adjustment I had the car smog checked and it was right in the ball park and passed. This procedure is in the Bosch fuel injection management book.