Slight smell when driving highway up hill...P0420

[Mikele82]

So last few weeks I would get a smell only while driving a highway uphill (not too steep). Faint smell like coolent fumes or oil burn...
can’t find any sign for leaks.
I did get a codeca few days ago P0420
And was thinking maybe some fluid is going into the CAT and burning hot ?
Any suggestions ?

XC70 2004

[abscate]

When your engine is working hard that's when the PCV. System is most taxed. Could just be a little blow by.

Did you mix brands of gasoline by any chance ?

[oragex]

As above, test first the PCV. It gets clogged at higher miles and may burn or leak oil at the PCV hoses (if cracked) or worse at the engine seals. It would smell burnt oil www.youtube.com/watch?v=gK8kUQxhT_8

The downpipe flexible also starts leaking at higher miles, it would smell like exhaust gases but a stronger smell because it leaks before reaching the catalytic converter. A little bit like rotten eggs.

[abscate]

A slight exhaust leak might be both the cause of the smell and the poor cat efficiency code P0420

That code is almost never the cat , by the way.

[Mikele82]

So I do get a good vacuum (as this video shows www.youtube.com/watch?v=gK8kUQxhT_8 )
and can't pinpoint any leak yet on pcv parts.
moving to check downpipe.
Any other suggestions?