Hi Guys, OK, so it's not a BEC so my knowledge is weak... it's my wife's old Mundaneo which has just had an MoT fail on CO emmissions (should be 0.30 max, it's 0.50). Lambda and HC are all good, as is the car generally. There are no logged fault codes, multimeter swings accordingly.
MoT guy said ECT (water temperature sender to ECU), but I don't think so. It goes nicely down to 1.3 Kohm and triggers the ECU to start the fan.
Following the Haynes checks, the EGR and all related vacuum piping are in good health. MAF has been replaced a while back, believed good. So... please... anyone, feel free to offer any experiences.

Haynes suggests Cat life is 50-100K miles, car has done 130K (30K this year). Cat can is intact, though clearly it's the car's original. Any experiences..?

chuck one of these in the tank Cataclean

if it works Yeh
If not its on £20

[Edited on 25/8/10 by tomgregory2000]

0.5CO is about what you'd expect to see with a non-working cat (or no cat) or even a cat thats not hot enough. I'd guess it's bu**ered. Try the fuel treatment and give it a good long blast down the motorway just before rtetest and it might revive. Chances are you need a new one though.

A good cat once up to temp will result in a CO of 0.0 if everything else is OK.

[Edited on 25/8/10 by adithorp]

OK, an update and thanks for the advice.

I ended up running a new catalyst, after trying just about everything else. Clearly the engine isn't in great health, but the catalyst just about coped (though it did get a tad hot). That new catalyst is now off the car, wrapped tightly and carefully stored ready for next year!

The games we play.

The cat's supposed to get hot it works better that way.

Does it go through any oil? Oil ruins cats