you soldering this? if not you should be.

strip the wires back till you have clean copper wire, new looking, not dull or brown, solder to that. use shrink wrap tubes to seal it up good too.

when i did my maf pig tail, i had 3 inches or less of wire till i was into the main harness.

if let go for a long time dry wire can travel a long way up the insulation.