Originally Posted by
oldford
The purpose of a cat is not to remove CO2 but to convert CO into CO2. CO2 is considered to be less harmful than CO.
Changing the post cat lambda will not change anything. The engine is running far too rich.
Is the exhaust manifold leaking? Then that would explain it.
What signal is the front lambda giving?
It went to Ford to be put on their diagnostic machine and they said the front lambda sensor was stuck on 0.8v rather than switching. They suggested trying a genuine ford sensor instead. No sign of the exhaust leaking either.
I fitted a genuine ford sensor and checked myself and from cold the lambda works fine for the first 5 minutes or so, the voltage is switching and the afr is good but then over about 10 secs the switching gets less and less and then the voltage just sticks on 0.8v so the ecu thinks it lean and puts more fuel in.
I have tried 3 or 4 sensors, two of which have come from other working cars and all do the same thing, I have an LC-1 wideband sensor so have monitored it from the tailpipe and it shows the mixture is fine to start with then when the lambda stops switchng it goes rich. I've no idea what could be causing this?