Which color wire do I tap into to hook up this gauge? Do I splice into the wire just down from the connector plug behind the intake manifold. How have others ran this wire? Haven't looked at it too close yet, maybe tomorrow.

 

Don't those run to the oxygen sensor?

--
Semper Fi
Cpl SH Won
Wpns Co, 2nd Bn, 24th Marines

 

Hook it up as close to the O2 sensor as possible, and ground the ground wire as near as possible to the O2 sensor to keep your meter as accurate as possible.

 

I tapped mine into the wire from the O2 sensor a few inches from the connector behind the intake manifold. This is the easiest location to work on the wire. I grounded directly to the battery to reduce interference. My A/F ratio monitor appears to work flawlessly.

 

Hey David, if you ground it nearer to the O2 sensor, or at least on the engine block your reading will be more stable, there will always be a volt drop across the main engine ground strap due to the load from the alternator. If you connect to the engine you read the O2 sensors output directly and not the output +/- the drop in the ground cable.

 

But isn't the ground for the O2-signal coming from the DME anyway (through the ground-strap)?

I can't imagine that running your own wire to the O2-sensor would give a cleaner picture than the stock coax-shielded cable. And if it does, then your DME is getting a bogus signal from the O2-sensor and your mixture should be off and the car should run like sh*t then?

 

Not sure if I understand the ground confusion here. I have *my* way of looking at it (eg. let's see if I can make matters worse ):

- The 3-wire O2 sensor uses the exhaust-block-ground strap-battery as a ground. This enters in the unstable readings that I have experienced with a run-of-the-mill air/fuel meter (autometer). This due to the thermally induced resistive changes as the exhaust and block heat up. (very visually evident/conclusive after you've watched the effects of this on a meter/gauge)
- Rather than do it properly, and install a four-wire sensor (my 3-wire was nearly new at time of install) I chose to run an external O2 sensor ground directly to the battery. I did this by attaching an automotive spring clamp to the O2 sensor shell, then running the wire up the battery.
- The provided instructions make it even easier to decide on the A/F gauge ground.... they said to go directly to the battery for best results. So I do... and seemingly complete the circuit of proper and consistent grounds. (believeing that this would actually improve the accuracy of the signal to DME is likely, but limited in usefullness... any disagreement?)
-so, now I have an O2 sensor ground to battery, and A/F meter ground to battery, and all is well with the world.

As I said, the visual I get from the Autometer A/F meter sells the whole story on reducing interference and bad grounds. The dither is much smoother, but admitedly, there's no real perceived change in engine operation.

Clear as mud?