Z3 2.0 exhaust lambda sensors.

[Pogo]

Hi. This is my first post. I recently bought a Z3 2.0 in the UK, and imported it into France where I live.
I have had an exhaust emissions problem with the Control Technique (french MOT). They guy suggests that there is a fault with either, the catalytic converter, two sensors mid exhaust, or a sensor at the front, engine end of the exhaust system, which must be high up as I didn't see it when I dropped the system off for a little welding.
My question is, are the sensors common to all Z3 engine sizes, or different for each? Are they left or right fitting, and would they be different for lhd and rhd cars?
Does anyone have any suggestions, or advice, or a method of testing them?
Thanks on advance

[bowei001]

When I changed the lambda sensors on our 2.0 (1991cc) I changed all 4. There are 2 before the cat, on the manifolds, I think. I believe that these are both the same and fit 2.0/2.8/ 2.2 & 3.0 and seem to be the same for both LHD & RHD.
The rear 2 are behind the cats and are different part numbers as they have different length cables. These are the same for 2.0/2.8 &3.0 and seem to be the same for LHD & RHD.
The connections are quite well hidden (it's quite a while age that I changed mine) but can be changed without dropping the exhaust system.
Check the price from BMW and then try a Bosch dealer as I found them considerably cheaper and the sensors I bought had both the Bosch part number and the BMW number and logo stamped on them (but that was in 2010). Be prepared for quite a high price from both places.
Have you checked the RealOEM website to see the parts diagram and part numbers? I find it very useful but always ask the dealer/supplier to check that the part number you give is correct as RealOEM does have a few errors (it sometimes thinks that the 2.0 is an M52 engine and not an M52TU and sometimes the parts are different).

[Mike Fishwick]

Before buying new Lambda probes, check the rubber inlet coupling between the airflow sensor abd engine for air leaks due to splitting. This weakens the mixture, and so causes the ECU to richen the mixture - hence excess emissions.