[laiman]

Hi all,
Had emissions checked just yesterday. Drove 17 miles to dealership and ragged it a bit on the way to make sure it was warm. Emissions was failed and ive attatched the data.
Car has recently had an oil change, oil housing gasket replacement and had new brakes. This past year its had the VCG replaced also, with new spark plugs and an air filter in January earlier this year about 3k miles ago. Results on paper look a little rich. There is sometimes a smell of fuel near the rear of the car, and the exhaust can have a faint white smoke. Thermostat and watercooler have been replaced 2 months back as well.

Dealer said it could be the o2 sensors which i suppose makes sense for the age but they need to bring the car in next week to look. How can I go about testing the car over the weekend to see what the problem is? Ive got a basic bmw scanner. Worried repair will cost more than i bought the car for.

[therealdb1]

Yes you are consistently running rich and your lambda values are a little low. I would expect them to be closer to 1.
Looks like the oxygen sensors are on their way out but not yet bad enough to trigger a fault code.
You don't say how basic your scanner is but if it is BMW specific it is more than a generic code reader so it should have some way of looking at live sensor data. You could also check the voltage across the sensors but by the fact that your car is not failing on Lambda but on CO that probably will not tell you much.
Replacing the sensors need not be a second mortgage. Any competent garage or even DIY mechanic could do it. As with many of these jobs access is usually the most difficult part of the task. I certainly would not take a job like this to a franchised dealer otherwise, as you say, the bill will be the same value as the car! Do you not have a local independent garage who could take a look for you?

[laiman]

Just went to take readings, got car fired up and waited a few minutes foe the idle to come down to 650. Oil temp at about 50.

Readings I got:
Both precat o2 sensors at 2.00v
Post car sensors 0.7V
Additional mixture adaptation bank 1 mg/ : 0.55
Additional mixture adaptation bank 2 mg/: 0.21
Multiplicative adaptation bank 1 : -4.57%
Multiplicative adaptation bank 2: -1.28%

10.5kg on the Air flow sensor at idle
Intake mani pressure 49.8hPa

Am i right in thinking its weird to see positive additive (short term trim) and negative long term trim? I though negative long term indicated rich and positive short indicated lean, am i misunderstanding the readings?

[Andystobbs]

Cat should be oxidising CO to CO2. I'd say CAT is below efficiency. Be worth a shot of CATACLEAN or similar before any other spends.

[Tambohamilton]

The cat can only achieve that if there is O2 present in the exhaust gas. If the engine is running too rich (possibly caused by bad lambda sensor(s)), there won't be any O2 available and therefore the cat can't do its job.

Sorry OP, I don't know enough to help with your O2/adaptation values.