Ocelot

I've got an Autometer A/F gauge that is being mounted on my a-pillar, and I was just wondering whats the closest wire to tap into to get a reading for it? The more detail on the wire, the better, instead of just saying the name of the wire, because I have no idea where it should be coming from.

1987RX7guy

iTrader: (3)

At the ECU I beleive the FSM has the pinout of the harness.

Ocelot

Anyone have a page # to look to?

1SxyRXy

assuming its a S5 it goes in the middle plug and i think its the 2nd pin on the top from the left i belive. its solid black. it should be around there.

elfking

I myself went to tap the wire for the O2 sensor at the ECU. Pulled out the pin, soldered to it. and it wouldn't fit well going back in, so I un-soldered it and put it back in. I thought about taping the wire further back, but really the previous owner already put a bosch universal o2 sensor on there.. which had a crimp connecter to the origional OEM connection...

So any chance of "shielding" would be lost at this point. I think im going to tap the o2 sensor at the green connector where it runs from the o2 sensor to the long wire which runs to the ECU. I may still ground it at the ECU, but playing with the ECU pins which have sat for 15-20 years are very brittle.

The three arguments I see for this being inacurate are:

1. People who say A/F is a waste of time.
2. Since im taping it near the o2 sensor and not at the ECU pin, that somehow 10 feet of resistance in the wire is going to throw off my entire reading.
3. After taping the o2 sensor it will become unshielded and not function as designed. (However universal ones on the car use a crim connection the the stock plug.

I tapped the pins for A/F on my 90 Eclipse and 83 Starion. And with my Starion I also tapped it in the engine bay becuase I wanted to test such an idea. The reading came out the same. (In that car, when you idle it hunts around bouncing into stoich and only goes into rich when you are boosting.)

This may be a personal thing, im just not one for ripping up the entire carpet, moulding, ageing plastic pieces which are already brittle.

Rather then sending a small wire through the firewall which has enough holes to shove anything through.

Again, some people will fight and say A/F is complete BS, not needed etc. At fault is the o2 sensor, no the car. However it came with my turbo timer, (Another thing people will fight etc.) but I figured I might as well hook it up. I may just tap the ECU plugs again, and the one in the engine bay so I can let you know the results.

People like to argue, with personal experiences. From what I have read from others here, "A/F is no good" even people saying "EGT is no good" however something I can use to keep track of my voltage/A/F will help, with a car that has no indicators when there is a problem with the charging system. I think that on the FC's (not sure on FD's) the O2 sensor being used on the Freeway only for gas milage, may make sense that its not needed. However with having it hooked up you can tell if suddenly you are getting 0 volts from your o2 sensor that it might be time for a new one. (Just examples here.) It will let you know when stuff has gone out of whack. Granted gas milage is not going to matter much in these cars... but I like to make sure my car is in proper working order so I can squeeze myself past the CA smog exams....

I'll post somewhere when i come around to taping both o2 ecu points to see if it makes a difference in our cars, in comparison to my Starion. I honestly doubt it though.

The FSM has pictures and diagrams of the pins to use for your ECU. My APEXi turbo timer had a picture of the pins also, but Id rather trust the service manual and use the APEXi one as one to fall back on if I must.

I hope this might be usefull to someone...

MtnRacer

Easiest, quick and dirty way to do it is to tap it in the engine bay, on the wire coming out of the o2 sensor itself.

Steve

rotorbrain

easiest thing to do is ditch the gauge and get a wideband unit. . . running afr's off the stock unit sucks. . . and so does the autometer gauge. . . you get nothing out of it. all it does is annoy you at idle and give you an inaccurate reading the rest of the way.

bottom line. . . get a wideband afr gauge

paul

Tofuball

Yes, easiest if you have a few HUNDRED $ lying around! What is an A/F metre, like, $20?? The cheepest widebands I've seen are like $300!!!

Unless you NEED this for constaint tuning, or have an ECU that can deal with it, then why waste the money?

If somone wants a gauge, it's still useful, even if you know the information isnt dead on, its still useful, even if at least to know what information your ECU is getting!

PS: Careful about tapping into the O2 wire itself. It has sheilding in its coat. Mine's already buchared and burned (retaining clip broke and the wire fell on the headers and now has no coating)

Ocelot

Yea, no way i'm shelling out the money for a wideband. I'm just going to use it to tell me simple details, and to fill my empty second gauge hole that I have another old boost gauge in at the time so it doesn't look like crap, lol. As for tapping into it, should I just cut the wire and solder it going in? Or is the shielding that delicate?

Tofuball

Its not that the sheilding is delicate, its that you dont want it touching the core wire or it will nullify the shielding effect; and make the O2 sensor less acurate by allowing it to recieve random electircal signals from the sheilding.

I personally would splice it in on the ECU wire to the O2 sensor as it is not sheilded, and is already inside the car. Its not that hard to get to either. Soldering it is a good idea

NZConvertible

You've slightly misunderstood the problems with tapping in at the sensor.

1. You've covered this one well.

2. The length of the wire is a complete non-issue, and I've never heard anyone say it's a problem.

3. The problem with the shield is not that it will become "unsheilded" (how would it?), it's that unless you're very careful when making the connection, you will make the shield contact the signal wire. Since the shield is grounded, you'll send the signal to ground, and neither the ECU or the A/F gauge will get a reading.

Less experienced people will not even know the wire is shielded, so they hack into it and then post here about getting no reading on their new gauge. That's why it's highly recommended to tap in at the ECU. You eliminate the chance of this happening.

These comments are based on ignorance. You shouldn't even be trying to measure AFR's on the stock sensor. That's not what it was ever designed to do! And the AutoMeter gauge is no different to any other one. They're nothing but a 0-1V LED voltmeter, and you'll get exactly the same reading whether you use a $10 DIY one or a megadollar Japanese one.

Your reading at idle shouldn't be "annoying" either, it should be steady. If it was, your gauge was correctly indicating a problem with your car...