Recently while splicing a generic 3-wire O2 sensor onto the stock loom I
couldn't get the solder to 'wet out' on to the wires (using commercial
grades of solder & paste flux).  What I did notice was that the wires are
*much* stiffer than ordinary copper wires usually are; they are silver
colored as if pre-tinned, but trying to scrape down to bare/fresh copper
didn't work-it was almost as if the wire was stainless steel!
Anybody else run into this situation - any solutions?

Austin