It might be something to do with the AFM I know we adjusted ours a few years back to solve an emissions issue.
Odd that it failed on Co level on the first test and the lamda was fine but on the second test the Co was fine but the lamda failed.
Personally I think I would be looking at the lamda sensor.
Sorry not much help, just thinking aloud.
Good luck.
D
I thought the same but the tester said not to worry about the second one as he can get the lambda in spec but couldn’t get the CO down no matter what
I’m wondering if you have an air leak in the exhaust. First fast idle shows high CO which means incomplete combustion, but the lambda is okay, in fact fractionally lean, so there ought to be enough air for complete combustion. Second fast idle shows the CO is okay but the lambda is much too lean. I once had a cracked exhaust manifold and that produced weird emissions numbers a bit like that. Sucking in pulses of fresh air before the lambda sensor made it run rich and created CO but the lambda of the mixed exhaust gases plus air looked okay on average.
So what changed between the first and second test? Did it cool off significantly, or something else. High CO is usually over rich mixture with poor combustion. You need to check the complete inlet and exhaust system to see if that is the problem. Maybe a dose of Redex will give you some clue as this will produce plenty of smoke!
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The lambda reading is still quite high even when it passed, 1.022 with 1.030 being the limit, only 0.008 off a fail. I’d like to see that nearer 1.000. I wonder what the tester did to bring the CO down for the 2nd fast idle test. If we’re ignoring that 2nd text result I’d suspect a catalyst.
Forgive me if my recollection is a bit rusty but a cat is an oxygen storage device isn’t it? If it’s not storing oxygen then this in itself can affect the Lambda reading can’t it?
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My thoughts were the same. Perhaps the joint where the aftermarket cat was fitted?
3rd time lucky. In the end I guessed that the aftermarket CAT that was installled in 2020 was probably killed after running the car with a bad lambda sensor earlier last year. I replaced the CAT last night, took it back and it passed straight away with CO down to 0.22.
Thanks for your help everyone 
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