While working on my beat up 89 CRX Si, I found that the 02 Sensor was cut off from the engine harness side. I see that the wire for the sensor is shielded (like coaxial cable), so I was wondering how I'd go about re-wiring the sensor back into the harness? Can I just splice into the inner wire, and not worry about the outer shielded wire?

Also, I noticed that the location of the sensor is on the bottom of the header, not on the top like the stock header, so would it matter if I extended the wire another couple of inches to reach to the bottom of the header? Thanks guys...

 

I think in this case your best bet will be to get a decent gauge "automotive" wire to do the extension, something from an autoparts store that has good shielding suitable for the engine bay...and put electrical tape and a wire loom over it to protect it.

As for extending the wires in length vs. stock. the only difference will be that the O2 sensor will take longer to heat up to its normal temp than it would in the OEM location, resulting in slightly crappier idle until the engine gets fully warmed up... but most of us with headers from DC and others have learned to live with that. A heated (3- or 4-wire) O2 sensor will get up to normal temperature quickly and remedy this, but like I said, its not really a terrible thing to deal with.

Good luck, take pics, post and share what you learn.