[Miketwovolvos]

Hi Everyone,
My 1999 1.6 s40 saloon's CO is stubbornly high >2%..
It's just run in really (155000 miles) and is fine otherwise. No codes with a standard reader, temp sensor replaced recently.

Original exhaust/cat, oil is ok but will change. The plugs are a bit old and probably need changing and I would buy a new aircleaner element for the next MOT, but all that will probably only have a marginal effect, I am thinking..

My main candidate for the cause is a slight leak between exhaust manifold and cat which is making it over fuel...but I have been wrong before... I could not find an obvious leak, but the downpipe is not very accessible, of course.
I know the downpipe is a sort of double pipe arrangement with 8 bolts securing it to the manifold.

Other possibilities include the cat, but they usually are OK and I have been recommended 'cataclean' but I am a bit sceptical about that.

Anyone else had this issue with an s40 this old and how did you sort it?
Thanks,
Mike