Wanting to install an A/F gauge, just not sure where to run the purple wire. I've installed them before, but on cars with only 1 o2 sensor, and usually 1 wire o2's.

So do I just run it to one o2 sensor? Does it matter which one? Which wire do I run it to?

 

You can run it to just one of the pre-cat sensors, or you can run a wire from each sensor harness signal wire to a single-pole/double throw switch, and use the switch to monitor either sensor. When you are all done, you will have a psychedelic light show, but not much in the way of useful info, other than an indication if there is a total failure of a sensor.

Drivers side sensor is the purple/white wire from pin C20 of the PCM. Passenger side sensor is the purple wire from pin C8.

 

What Fred is saying is the pcm constantly varies AFR even at cruise which is how it keeps tabs on wether the O2s are working this will result in constant flickering fvrom rich to lean. Then at WOT the stock narrowband sensors are meaningless, it will say rich but that will just mean richer than 14.7 and there is a lot of room between 14.7 and correct. 14.7 is the ONLY AFR the stock O2s are accurate at besides that they can tell you richer or leaner but not how much richer or leaner.
So like he said nothing but a light show. On a carbed engine where cruise AFR will be steady these could be useful.

 

My buddy went wideband on his rx7 and was going to sell me his autometer phantom for 20 bucks.

I guess i'll just pass on it.

It was fairly accurate I guess on my 87 conquest. Pointless on an obd2 tho eh?

 

How do you know is was "accurate"? There are no A/F ratio calibrations on it, other than "lean" and "rich". Has nothing to do with OBD-II. Its the result of how the PCM controls the A/F ratio in closed loop, constantly varying the ratio from lean to rich to allow the cat(s) to function. Then when you go WOT, the stock narrow-band O2 sensors are not accurate at the typical A/F ratios you want for max power/torque.

I don't know anything about how your 87 Conquest controlled A/F, so maybe it worked in that, but its not going to provide you with much info in an LT1.

 

Fred, I've seen these aftermarket 1wire o2 sensors like for carbed cars. Could you pop one of those downstream of the factory sensor and let it moniter stand alone like.

 

It would still be using a narrow-band sensor, and would still be limited by the wildly swinging A/F ratio in closed loop, and sensor accuracy at WOT. You need a wide-band sensor and controller to accurately read A/F ratio beyond the narrow-band sensitivity of 14.6-14.8:1