Arlen Holder wrote:
> Car is just bought by a kid just learning to drive (he's 16).
> 2004 Mitsubishi Lancer ES
>
> Neighbors asked me to teach him how to replace the oxygen sensor (due to
> emissions code).
>
> The threads were stripped and "filled" with some kind of hardened "metal
> paste".
>
> The new part is a Denso 234-4739 (marked 485000-4060, 07U05)
> The old part is a Denso (marked 234000, 8643, 07E23)
>
> What would you suggest?
> - Tap the threads? (22mm hex nut)
> - New exhaust manifold?

IF it were my car and IF the manifold is steel, I would remove the manifold,
then remove the square nut, and weld or braze in a thin-ish nut of appropriate
thread size.
If no thin-ish nut is available then make one with the dremel.
The sensor needs to be in the flame and also have good thermal conductivity to
the manifold.