i picked up an 84 z28 (real clean) and the 02 wire was cut. i came on here and people told me it was a purple wire i was loking for in the harness.

so i go to the junk yard and find a thirdgen (late 80's maybe) but it has the 02 hooked up and i cut it back as far as i could. i cut it at the firewall where it comes out of a t section with the a/c and temp wire.

here's my problem........... i cant find the purple wire to connect this to. my car has an 02 sensor from the factory (its a feedback carb 305). but on my car there are only 4 wires in that part of the harness 1 green 2 black (those go to the a/c/ then 3 is green (to the temp sender) and the 4th is blue NOT purple and it has been cut by someone. so was the 02 wire blue in some years and purple in others and im looking right at the correct wire? if not, what the heck is this blue wire to?

and i have pretty clear access to the harness because i took the manifolds off to put new gaskets and painted the block while i have them off so i can see clearly that its not just hanging there hiding.

 

O2 is purple

Its possible you're looking at the wrong area. Check the ECM pinout and trace from there