Checking mixture with O2 sensor
 

I have a '78 which does not have O2 sensor, but my catalytic converter has the plug to put one in. I need to adjust my mixture at idle , because I failed emissions for high HC. Normally, this is done with a CO analyzer, but they are expensive.
I know the AFR should be 14.7, which reads ~ 0.5V on a O2 sensor. So my plan is to buy a 30 bucks O2 sensor, plug it to the cat, and read if I am rich or lean with a multimeter.
Has anyone tried this? Seems like a good way to set the mixture...

Aurel

I searched the archives, and two people have asked the same question already without getting an answer. It means we may be on uncharted territory here. Me likey!
Here is the plan: I will try to read the oxygen sensor directly through the USB port of a laptop via labview. And with labview, I may be able to record and convert voltage to AFR ditrectly!

Aurel

"...the main problem with any narrow band O2 sensors is that the ECM only knows that the mixture is slightly richer or leaner than 14.7:1. The ECM has absolutely no idea as to the operating A/F ratio outside the stoichiometric range. In effect it only knows that the mixture is richer or leaner then stoichiometry. An O2 sensor voltage that goes lower than 450 mV will cause a widening of injector pulse and vise-versa. The resulting changing or cycling fuel control (closed-loop) O2 signal is what the technician sees on the scope when probing at the O2 sensor signal wire."

http://en.wikipedia.org/wiki/AFR_sensor

You want a wideband sensor and controller. Buy or borrow an LC1 and you can plug that into your USB for monitoring, logging, etc.

Check this post out.

http://forums.pelicanparts.com/showthread.php?t=179654&highlight=fuel+air+mixture +sensor

I used this method the other day. I wish I could get a hold of a gas analyzer to check how accurate it is.