Checking A/F Ratio on your car?

[ra23celica]

Is there any way you can check what voltages the oxygen sensor is sending to the ECU while your car is running?
I have a single wire O2 sensor on a 1989 1G-GZE.
I know that it should vary rapidly, but can I get some idea if it is always rich for example?
Can you plug a multimeter into the diagostic port and get a reading from there - and if so - how?
Thanks for your help.
Cheers,
Mitch.

[andy]

a mechanic used a snap on computer to test my oxy sensor. i have a 4 wire, and it pulsed 8 times a second, so no ordinary multimeter will do. you would need to view the history on a graph type display.
but all he did was plug this thing into the back of the oxy sensor, so you should be able to do the same thing with a multi meter, just dont think the read out will give you any usuable info. i guess you could set it to give you the max readout....

[JetspeedCamry]

Hmm..well, ive got an Autometer narrowband AFR guage. It seems to work fine...all it is really is a voltmeter, 0 to 1 V scale i believe. Mines a 4 wires too.
Ive seen people use multimeters on one of the wires to check the voltage, and from that, you can get an "idea" of the condition of the o2 sensor. It's by now means like a wideband reading though!! but, its something. You'll basically know if you engine is running LEAN, STOICH or RICH.

[-==L=a=N=c=E==-]

This leads me to the question.

Before the use of oxy sensors. How did one tune the AFR? smell sound or hope for the best?

[JustCallMeOrlando]

There have long been oxygen sensors, just not always in cars. That, and a lot of stuff was tuned by ear (i.e. sounded the "healthiest" without pinging)

[chris davey]

read the plugs

[Norbie]

Yup, the old-schoolers would just shut off the engine and pull out the plugs. You can sorta tell by the colour/condition of the plugs what was going on when the engine was shut down. The colour of the exhaust deposits on the inside of the tailpipe is also a clue. Oh and exhaust temp in the manifold.

[JetspeedCamry]

The colour of the exhaust deposits on the inside of the tailpipe is also a clue.

Indeed. My dad used to do this all the time, after every drive..
It goes something like this...

for a LEAN condition.
for a generally good burn, STOICH, i guess
for a RICH condition.

If it's really rich, it can leave black sooty deposits in the pipe, and of course, black around you bumpers

[ra23celica]

Thanks for the response everyone. I have been looking at the spark plugs and sniffing the fumes and I remembered that the 02 sensor cycles 8 times a second, so my crap multimeter will be no use to me at all.
Think I will go and have it tested and see what numbers it produces.
Cheers,
Mitch.

[urantia]

Another method is to use an old analogue volt meter, the ones with a needle that respond to quick voltage changes to get an idea of whats happening in real time.

[MacroP]

Thanks for the response everyone. I have been looking at the spark plugs and sniffing the fumes and I remembered that the 02 sensor cycles 8 times a second, so my crap multimeter will be no use to me at all.
Think I will go and have it tested and see what numbers it produces.
Cheers,
Mitch.

You need a high end Multimeter like a Fluke 87 or similar that can do MIN/MAX/AVG readings over a very short period of time. These can be used to test the Ox terminal on your DIAG connector. I recently put this to the test on a friends car and it works. 0.2MIN, 0.6 MAX and a 0.45volts average. Spot on.

[SilverGhost]

This leads me to the question.

Before the use of oxy sensors. How did one tune the AFR? smell sound or hope for the best?

Didnt they have 'exhaust gas analysers' that they stick a probe into the exhaust pipe, or in the EGR pipe to get a reading of CO or HC content, by this they could tell what a/f the car was running, or was that just a precursor of an O2 sensor?

[Norbie]

Exhuast Gas Analyser typically means wideband oxygen sensor along with other stuff (eg CO), but I don't think these were in common use until the 80's.

[SilverGhost]

fair enough...though 80's is old for me!

[30psi 4agte]

They used to / still do use EGT ( exhaust gas temp ) to give an indication of how things are going