Home made A/F monitor
 

I used to hook-up a digital voltmeter to one of my 02 sensors to monitor A/F at wide open throttle, anyone ever do that?

It is very helpfull.

how did it work? explain more about how you hooked it up and what readings mean lean and which are rich.

thanks,
adam

O.K. I did this 10 years ago, so I'll try not to leave anything out.

Digital Voltmeter positive to computer return wire on 02 sensor, (there are 3, 1 is ground, 1 is 12 volts as a pre heater, and the other is return), Voltmeter black to ground (shorter the better)

You will have to probe your 02 wires to find the return signal, you need to have the car running, it will be constantly changing, this is the computer trying to constantly achieve the perfect Stoichometric A/F ratio which is 14.7:1, when you put your foot to the floor those readings will freeze on the voltmeter display, THAT is the voltage being sent to the computer, and it interprets from there.

If I remember right, as far as Rich/Lean, anything above .50 volts is getting rich and below .50 volts, things are getting lean. ALL 5.0 run rich from the factory, so when the 17 year old kid buys a brand new 5.0 and drives home at 110mph the engine has plenty of fuel so you will see rich readings I'm sure, I did it because I was using nitrous. My readings were around .47 volts on the spray.

I always put real small baby pins through the 02 wires insulation to get at the wire, this insulation is very hard, and the wires are very small, if you mess one up your screwed, the less you play around with these wires the better, then I taped my positive wire from the voltmeter to the baby pin. I grounded the voltmeter in the car real short.

Try that. Oh! and tape everything up nice when you get it right, this will keep water from screwing with the electronics of the car, make sure you get a good SHORT ground too, an interior screw is what I used I think.

Hmm, My car's carbureted but I've got O2 sensors plugging the holes in my X-pipe, I might have to do some testing and see if I can build a cheap carb tuning device!