Hi all, my MY97 V3 STI failed MOT on emissions, high CO (1.8%) low Lambda (0.94).
Have changed the usual two suspects namely Lambda Sensor and Air Mass Meter which resulted in absolutely bugger all difference.
Have de cat centre but had this fitted last year and was bang on the money at last MOT.

Anyone got an idea as to what it could be?

Car drives brilliantly with only very slight hesitancy on part throttle around 3k rpm.

Thanks in advance,

Glenn

 

Mine recently failed the emmisions in February, I changed the K&N back to the original airbox and it sailed through, If yours is already fitted with a standard airbox, then it looks as though your downpipe cat is starting to fail, either change this if possible, or better still put the centre cat back on which would be an easier task.

 

Its either not been warmed up properly or the cats f***ed

 

Cheers guys I have to say thats the direction I'm heading in.
HC also up a tad just on 100.

 

Only change from last year is that I fitted an A'pexi induction but took it all off and put standard airbox back on after failure.....no change!!
Interestingly, forgot to mention that CO can be 3.3% with Lambda 0.90 or 1.8% with 0.94 lambda.
Depends on what mood its in!
Can report that it was def warm enough, did several tests on my gas analyser last sat and even went through fine on one occasion!
Am a little foxed by this, can a cat **** around this much?

Can't hear rattle etc but maybe cat just not working anymore.
Have only ever come across this once before, usually cats are blocked, partially blocked or in bits.