S40: - High CO, everything else OK 1999 1.6 s40

Miketwovolvos · Apr 5th, 2024, 13:49

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

Apr 5th, 2024, 13:49	#1
Miketwovolvos Miketwovolvos Last Online: Apr 26th, 2024 17:14 Join Date: Apr 2015 Location: Birmingham	High CO, everything else OK 1999 1.6 s40 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

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