Tom M'Guinn

Is there a correct way to route the O2 sensor wire/harness? I ask becasue it seems to run very close to the exhaust -- cross-over/downpipe. I seem to recall the shielding and wires are made for heat, but want to make sure there is not some trick that will get the wire behind a heat shield or something. I cannot see anyway to do that, but thought I'd check...

still prepping for CA smog....

hosrom_951

If you are concerned about the wire getting hot, you can get some thermal sleeve made specifically for wires in the engine bay.

Lindsey sells some of these, heard that they are pretty good.

Tom M'Guinn

I thought about that -- even have some laying around -- but don't want to re-engineer it. I just wondered if there was a "correct" way to route the factory harness?

Danno

On the stock configuration, it goes next to the air-oil separator underneath the heat-shield. It then pokes out and does a short 6" run to the bung on the crossover pipe.

kasturbo

Danno, doesn't any aftermarket chip pretty much bypass any o2 sensor input? So does it even matter if it's working or not?

eclou

I don't think it is humanly possible to route the sensor the stock way unless the shields are removed (i.e. you have the turbo out)

ninefiveone

It can be routed that way but it doesn't seem intuitive at all the first time you try it. The first time I did the O2 sensor, I routed it differently and ended up with a melted harness. The second time I had the intake manifold off and that made it a lot easier to see where I wanted the wiring to go.

Ideally, you want to use the original harness to pull through the wiring for the new sensor so that it traces the factory route.

Danno

Yeah, I dropped a string with nut at the end down between the air-oil separator and the heat-shield. Then I tied the string othe O2-sensor plug and pulled it up.

"doesn't any aftermarket chip pretty much bypass any o2 sensor input? "

Nope, they all use the O2-sensor. It's a hard-coded algorithm in the DME program-code itself, the chips just change the data-tables of fuel & ignition. The O2-sensor only enough significance to change the air-fuel ratios slightly, so the chip-mappings have to be within range of the corrections (dithering above and below the map).

What happens when O2-sensors fail, is that they read too lean all the time, thus the computer will increase fuel. This tends to cause overly rich mixtures and stumbling. Quick test is to just unplug the O2-sensor and see if the car runs smoother. If it does, your O2-sensor is bad. A working O2-sensor won't change the car's behavior much, either plugged in or not.