A/F meter hookup, tap into O2 sensor

[SQF]

This proceedure is for 87+ cars.  The wires are not the same in older model years.  Those of you who have older electrical manuals please look up the wiring color and position on the ECU and email me so I can add them!!

 

Here is the directions mike c. posted on the old boards to hook up your A/F meter.  

This post covers ONLY how to connect to the O2 sensor for the best read.  Considering mike c's background and experience I agree with this install.  I have seen gauges running showing 4 bars at a time.  My gauge runs 1-2 bars.  That means a more accurate reading.  Here you go...........

 

The best way to tap into the O2 sensor is to:

1) key out of the ignition, unplug the battery.

2) remove the connectors going to the ECU.

3) near one corner of one the large ECU connector you'll see the O2 shielded wire. There is another shielded wire on the other end of the connecter - actually IN a corner - DON'T USE THIS ONE! That is your tachometer signal to the ECU. Anyway, on the shielded wire for the O2 sensor (it'll have green+red and yellow+black wires on either side of it) tap into the O2 signal at the connector pin. This way, you have the shortest wire possible to your A/F guage and you are well away from the noisy ignition system. You don't need a shielded wire to your A/F guage this way.

mike c.

also.....the ECU has a seperate ground signal which goes to the TPS,ISC and coolant temp sensor plus a few other misc things (check your wiring dia,its pin 4 on the ECU I believe). to get an ACCURATE reading on your A/F YOU NEED TO USE THIS GROUND.......this is where I tapped my ground for the A/F, I used the coolant temp sensor. A/F seems to react slightly quicker and now I know its accurate

 

 

IF YOU HAVE ANY QUESTIONS ABOUT THIS POST OR THE INSTALL PLEASE DO NOT POST HERE, POST ON THE VIRTUAL MECH FORUM AND SOMEONE WILL CONTACT YOU.

THANKS, SQF

[xtremesushi]

here is a good question, im running 19 psi, 1gmas,apex avcr, modded 12a flowing about 500-540 cfm. i hooked up a new air fuel(autometer lunar)guage and i have a new mitsu o2 sensor. its reading rich at idle and full boost. it drops off completely at deceleration. is this the way i need it to read? :-/

[JAinsworth]

Follow the shielded O2 wire about 6 inches up from the ECU connector.  It will not be shielded there.  Splice and solder in your gauge wire there.

Jimmy

[Funky Phil]

here is a good question, im running 19 psi, 1gmas,apex avcr, modded 12a flowing about 500-540 cfm. i hooked up a new air fuel(autometer lunar)guage and i have a new mitsu o2 sensor. its reading rich at idle and full boost. it drops off completely at deceleration. is this the way i need it to read? :-/

 

Yes, That should be fine. It should also drop off when you shift especially if you have an atmosphere BOV. And I might as well say it before someone else does. The only A/F worth really haveing is a wideband A/F.

I have a question though. I had my A/F istalled and working. everything was hooked up within the cabin except the O2 wire which went through the engine bay to the sensor where I splice in. Everything was good for nearly a year then it just stopped working. I disconnected everything and had a buddy sit in the cabion while I reattached it and we found that the only time the gauge would work was with the ECU disconnected. Every time I would touch the ECU wire to O2 and A/F it would kill the guage. but I also noticed  that idle wasnt changing when i connected and disconnected the ECU like use to do. Now it runs rich as hell and I know its killin performance. Is that my ECU messing up or what?

[Syth]

SQF, i have a question about this:

"the ECU has a seperate ground signal which goes to the TPS,ISC and coolant temp sensor plus a few other misc things (check your wiring dia,its pin 4 on the ECU I believe). to get an ACCURATE reading on your A/F YOU NEED TO USE THIS GROUND"

 

I do not have a wiring diagram for my car (88) and i was wondering if you know exactly what pin you used for your ground?  I am putting my A/F guage in my car on Saturday and really don't want to screw up my ECU or something so i am asking questions before i do anything.  Thanks in advance for any and all help.

 

Also when i find that pin, can i just ite the ground wire from the guage right into the wire from the pin or actually solder the A/F ground to the pin also?