Just took the e30 325i out after 3 years to get it mot ed and it failed on the emissions saying the co2 is too high on norrmal and fast idle and lambda
The car nas been sitting for a while and is due a service as it ismissing slightly, but its been like that for years and passed last time with no issues.
What do i need to do to get the co2 down?.
Ive got ten days to sort it!!
Thanks
CO2 high -failed mot on emissions - how do i bring it down?
Moderator: martauto
- Brianmoooore
- E30 Zone Team Member

- Posts: 49358
- Joined: Mon Jan 10, 2005 11:00 pm
CO or CO2? Very different gasses. Also, what are the other gas results? You should have a printed sheet from the test station.
It was CO brian - il put up the emission test sheet.Brianmoooore wrote:CO or CO2? Very different gasses. Also, what are the other gas results? You should have a printed sheet from the test station.
Tester says it smells of fuel so probably running rich.
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- Brianmoooore
- E30 Zone Team Member

- Posts: 49358
- Joined: Mon Jan 10, 2005 11:00 pm
What's the date of first registration for your car?
- Brianmoooore
- E30 Zone Team Member

- Posts: 49358
- Joined: Mon Jan 10, 2005 11:00 pm
This is where things get complicated! Note the passage below, which is taken from section 7.3 of the current MOT manual.
"Vehicles fitted with a different engine must be
tested to the requirements of whichever is older, the
engine or the vehicle.
e.g. A 1995 car fitted with a 1991 engine (of
whatever make), test to 1991 standards for
emission purposes.
Note: The onus is on the vehicle presenter to prove
engine age
Has the M20 engine been installed with a cat. and lambda sensor in the exhaust system?
Do you know the age of the M20 engine? If it was made before 01/08/1992, then the testing limit for CO on your engine is 3.5%.
An exhaust that smells of fuel can indicate either a rich or weak mixture (with weak mixture, fuel fails to ignite, and passes straight out of the exhaust), but high CO does indicate a rich mixture.
"Vehicles fitted with a different engine must be
tested to the requirements of whichever is older, the
engine or the vehicle.
e.g. A 1995 car fitted with a 1991 engine (of
whatever make), test to 1991 standards for
emission purposes.
Note: The onus is on the vehicle presenter to prove
engine age
Has the M20 engine been installed with a cat. and lambda sensor in the exhaust system?
Do you know the age of the M20 engine? If it was made before 01/08/1992, then the testing limit for CO on your engine is 3.5%.
An exhaust that smells of fuel can indicate either a rich or weak mixture (with weak mixture, fuel fails to ignite, and passes straight out of the exhaust), but high CO does indicate a rich mixture.
Aah now that helps...i think i remember telling the previous testers about the engine change but i didnt know they adjusted the test to suit...
So if i go back to the same place and tell them, they should adjust to suit the earlier engine and should pass?
So if i go back to the same place and tell them, they should adjust to suit the earlier engine and should pass?
- Brianmoooore
- E30 Zone Team Member

- Posts: 49358
- Joined: Mon Jan 10, 2005 11:00 pm
If there's no Cat., then you'd struggle to get it down to the post 7/92 limits.
Note that the onus is on you to prove the engine age. An old test certificate with gas results sheet would probably do, if it's passed before.
Most M20B25s were pre 8/92 of course, since saloon production had finished by then, and only cabs. and tourings were produced for about six months afterwards.
Note that the onus is on you to prove the engine age. An old test certificate with gas results sheet would probably do, if it's passed before.
Most M20B25s were pre 8/92 of course, since saloon production had finished by then, and only cabs. and tourings were produced for about six months afterwards.

