Sad day for my subaru impreza MOT failure on emissions.

Everything else passed but the idle CO2 levels. When revving the CO2 levels were excellent.

Has anyone had the same thing happen? What was the cure?

Lots of people say the oxygen sensor by the CAT or the air flow meter. Is there anyway of testing either of these things as both are expensive to buy when i am not sure. Please help I have minimal time before my MOT totally expires.

Thanks

 

The AFR on idle is controlled by the ecu through the lambda sensor (the oxygen sensor), so this is you most likely cause (provided you have the Catyllitic converters in place). You can get cheap lambda sensors which are bosch parts but you need to wire them in yourself. It's not hard though.

 

Use the "Search" for MOT.

Nearly always Lambda, or MAF in that order.

MB

 

thanks for the reply, Any ideas on what part code it is from bosch or how i can find out?

I have ordered a MAF as I have checked the fault codes on the ecu and it is putting out code 23 which i believe to be MAF or MAF circuit.

I will fit this today and get the car tested tomorrow hopefully so if it is no better shall be going to get an oxygen sensor.

 

Reset the ECU after fitting, should work straight away but a reset is always good.

MB

 

Here goes nothing, gonna fit the new maf sensor now, am i correct in thinking that to reset the ecu i connect the two black cables and two green cables below the steering wheel? If not how do i ensure that i reset the ecu?

 

DAM IT.
The poor scoob idled a bit funny and seemed happy, just taken her for a spin and broke down 3 times in a mile. Engine went all lumpy as if not firing and then decided enough was enough. Limped it home, wouldnt even idle by the end. down to 100 rpm up to 1200rpm down up.
Think I shall be sending that one back then.

Anyone think that I would be better off getting the lambda sensor before i try and get hold of another MAF???

Any ideas will be greatly appreciated.