W126 Carbon Monoxide Emissions

[weathersone]

420 SEL failed MoT on emissions.
Described as "minor, just needs adjustment", no figures given.
How can this be rectified?

Have been advised the mixture is adjusted thru' the air cleaner, is this right and if so what adjustment will give the desired effect ie MoT pass?

Hoping someone out there has had this problem.......mw

 

[219]

Have been advised the mixture is adjusted thru' the air cleaner, is this right and if so what adjustment will give the desired effect ie MoT pass?

Yes , that's right .

Just behind the wing nut in the middle of the filter cover , you'll see a small grommet with a hole in the middle . You'll need a l-o-o-o-n-g allen key to insert here ( sorry - can't remember the size - but smallish - 3mm give or take , been a while since I did this ) and reach down to the mixture adjustment screw ( needs to be done with the filter in place as this affects the mixture )

by the way , have you changed the filter ? An old , blocked filter will cause a rich mixture ! If the filter is old and choked this might just be the problem - either replace or blow out with compressed air .

Anyway , with the car warmed up and idling , turn the screw ( can't remember which way ) until the car just about stalls , then back it up a touch . This should see you on just about the leanest mixture the car will run properly on .

Ideally a CO meter stuck up the exhaust should be used ( if you know the correct spec to set it to ) but otherwise the above is a good place to start .

 

[weathersone]

Sorted!

420 SEL failed MoT on emissions.
Described as "minor, just needs adjustment", no figures given.
How can this be rectified?

Have been advised the mixture is adjusted thru' the air cleaner, is this right and if so what adjustment will give the desired effect ie MoT pass?

Hoping someone out there has had this problem.......mw

Sorted
Car passed MoT today, was congratulated by tester on managing to get it spot-on without CO "gauge". Sound advice, thanks.............mw