Mercedes W123 K-Jetronic running rich

Firstly, I would give the car a thorough service, starting with a compression check and checking all settings such as valve clearances etc. Only then would I start looking at fuelling settings - plus if you don't have access to a gas analyser then I would take it a knowledgable friendly garage that does, you'll never get it spot on without one.

Let us know how you get on.

Cheers Guys, I am away at work for another 2 weeks but will scope it out when I get back. I have already done a compression check and all cylinders seem good and very little difference across all 4. The car runs sweet as a nut without any other issues apart from being overly rich, idle is maybe a bit low as it wants to cut out when its cold, its fine when warm though, just a bit rich smelling.

Oil/filters etc are all good and new. plugs were not too bad.

I have access to a gas meter it reads CO in PPM rather than %vol though.

I Will check the vac hoses first, as I noticed another couple of hoses were a bit perished looking.

Also check the warm-up or cold-run regulator (google should deliver a how-to). This enrichens the mixture for cold start and during warm up. If it's broken, it's enriching the mixture all the time... If this checks out solid, the K-Jetronic can be adjusted, it's only the KE-Jetronic where you should not touch the CO-screw... But check the whole system first, especially the warm-up regulator.