Air fuel ratio guage

S

ScottSimonsen

Registered User
I bought an autometer air fuel ratio guage and i hooked it up to the pass. side o2 sensor. Well i found that the o2 wasnt ever reading more then .100 volts so i replaced the sensor with a new one from ford they are both 3 sensors. Same part #. But now i dont get any signal. Has anybody else had this prob. and how did you fix it.
 
I have heard that you should put a separate one in and hook your a/f meter to it alone,from what i was told it would throw off the readings if you hooked it up to one of the existing ones.
 
im not worryed about that. Right now when my car is running and my engine its at operating temp i get no signal at all. The only thing that i get is 12v power for the o2 heater wire. The o2 sensor should make its own voltage but nether do. And one is brand new.
 
AF guage

I have a guage too and couldn't get it to work by hooking it up to my O2 sensor. When I asked a friend about it who knows a lot about that kind of thing, he said that our O2 sensors don't read enough variables to make a guage worth while. If you could hook a guage to a wide band O2 sensor then it would tell you something but he said that our stock sensors are almost like idiot lights, it reads good, rich, and lean but nothing in between.
 
i dont think thats right. When an o2 sensor reads rich its at like .5v and when its lean it reads around .1v. I took a dvom to the signial side of my old o2(when it was still in the car) and it read .098v at idle and when i would step on it it would go up to .110v. One time when i was holding the Rpm's around 2200 for a while i got the o2 to read .4v and the air fuel gauge work correctly. Also SkySc did you ever get your guage to work and how? By the way thanks for the help
 
Last edited:
maybe not

i have a gauge, but haven't hooked it up yet.

anyway.
the sensor should give off plenty of values.
when checking O2 sensors, you should get readings like the following... .2... .7... .3... .7... .1... .9... .4 etc.

a good O2 sensor ,and properly running car should keep sending signals on either side of .5. thats how the cars keep stoich. below.5 is lean and .5 and up is rich. then the computer keeps adjusting the flow of the injectors.

You might try running sheilded wires up to the guage. theres a lot of electrical things that can affect the wire going to the guage, and you're talking about very small values, very little amperage.

somebody should come in on this post soon, and say that have it hooked up and everything works fine, because there are quite a few SCer's with A/F guages.

jim
 
Okay I'll be the one I have one and it work. I bought the car from someone who apparently wasn't smart enough to hook it up because it was in the gauge pod and was not hooked to anything. Anyway the thing is running off the drivers side wire on the cars wiring not the O2 sensors wiring harness. It is an autometer and lights up fine but it does fluctuate all the time. I have a 95 5-speed and I think it is hooked up to the grey/light blue wire . You can see the computer adjusting the mixture all the time it tends to bounce back and forth while at an steady throttle position. When you go to WOT it goes to rich/green and if you let off it goes to red/lean then the computer will compensate and go back to stoich. It was a novilety at first but now has lost some of it's glitz and gets ignored. If you were adjusting your fuel pressure for racing it would be great though.
 
I got it working today. I was tapping into the wrong wire. I have a 89 Sc and it was the black wire. Thanks for all the help.
 
where can I obtain a AF guage?

Where can I buy a AF guage? Is it at any auto parts dealer? I would like to know if my O2 sensors are bad.
 
AF gage

I haven't gotten mine to work yet. I got it at summit for around $30. I've got it tapped into the grey wire on my 91SC. Can I tap into a wire or will I have to run a seperate O2 for the gage?
 
no need to run a seperate sensor just look at a wiring diagram from chiltons and fing the O2 sensor wire that runs from the sensor to the PCM and look at the wiring harness just above where the plug for the sensor comes off. Chiltons will give you a color for the wire becuase there will be 3 or 4 wires in the plug just locate the appropriate color and splice in.
 
i was having fun checking my o2 with a volt meter on a test ride i just tapped in to the black wire on 02
my meter is not real big or accurate but it was interesting to see how they work

mostly i was lean to good .5 volts at anywhere from 0 volts going downhill with egr open coasting at 55 mph it would go down to about .2 volts
cruising it would stay near.5 volts and at idle near .5 volts and when in boost it would go as high as .8 volts at wide open they said it would go to 1.0 on wide open so im running pretty good at least on left side i never went over around 3500 rpm it may go higher at higher rpm i didnt test right side yet
 
Last edited:
DO NOT USE CHILTON'S WIRING DIAGRAM, chilton's tells you to splice into the tan/orange wire, i believe. That is the HOT (12v) wire. using a splice connector (the little blue ones, that clamp closed) tap into the black wire on the o2 sensor. As stated above, use a shielded wire... and make sure it's up and off of the exh manifold trust me...
 
i believe tan an orange is the right colors on mine that hooks to black wire on 02 black plug and tan and red for other side
 
It's safer to tap into the wire coming off of the o2 sensor itself. It's easier to change a sensor, than have to re-wire the harness, because you accidentally cut a wire. =\
 
You must log in or register to reply here.
Back
Top