Quote:
Originally Posted by canis
From 1999 onwards these cars had two lambda sensors, one before the cat and one after. The one before the cat is used to adjust fuelling. The one after it is used to assess whether the cat is working. And that's why it's become law, I reckon, to stop people running de-cat.
Now, whether that's the cause of your high CO, I don't know. I'm not entirely sure how a cat works, to be entirely honest. I'm guessing it's no longer performing it's chemical function and not scrubbing the air, or something? And the fact it's failing at this task is being detected perhaps by your second lambda sensor and putting the light on. But this is speculation, I'll admit.
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Sorry to ask this here but the citroen forum isn't very good and you sound like the man who would know the answer.
My 1.1 saxo desire has high emissions trouble, started a few years ago when the front of the exhaust failed and fell off and had to replace the front part of the exhaust which is a cat straight off the manifold and a down pipe to the bottom of the engine. Theres an o2 sensor on the manifold and one in the front section just after the cat.
The cat was replaced and the whole remaining exhaust was changed too. After a while my engine management light came on and it was due to inefficient catalyst efficiency. I reset the light and put it in for MoT and it only just passed on emissions. The next year it failed on emissions so I replaced the cat and it passed with flying colours.
Similar time to the first replacement later and my engine light came on again. I managed to get the light off with some Tesco 99 and an Italian tune up but it has since come back on again. I thought the garage had put a cheap cat on the car but since it came back on a similar amount of time after another cat I started to wonder if it was a damaged o2 sensor and was looking to get some but they're expensive and makes the car less economically viable.
I appreciate this is the wrong forum but the correct forum is useless and this s40 section is the best forum I've been in. Thanks for your help!!!