deterioration exhaust emission values warning light

[Jose Magalhaes]

Been having problems with the deterioration exhaust emission values warning light in my Z3 1.8 for months now.
The light first came on about one year ago.
Car runs normal, no misfire, no power loss, nothing – just the light remains on.
Took the zed in to the local (Portimão, Portugal) BMW dealer.
First, they adjusted part 12147518628 (Camshaft sensor); light came on again shortly thereafter, so they changed part 12147518628 (Camshaft sensor); light came on again shortly thereafter, so they kept the car for four days, eventually changed Part 13721247404 (Air filter element); shortly thereafter – you guessed! – the light came on again.
The zed is going in again…
I found an interesting article here:
http://www.ronstultz.com/knowledge/Documents/BMW Z3/BMW Z3 - Check Engine Light (CEL).htm
Ron Stultz says “If the car is running fine with no symptoms other than the CEL, it has been my experience that this means either an fuel system vapor leak or there is a problem with the catalytic converter (CAT)”; it seems to be my case.
Anyone with a similar experience? Any ideas?

 

[GazHyde]

Out of interest have they read the fault codes at all, and does it give a particular code?

 

[t-tony]

An exhaust gas emission test might shed some light on the problem too.

Tony.

 

[Jose Magalhaes]

Out of interest have they read the fault codes at all, and does it give a particular code?

thanks. they say they did, but did not give me the codes.

 

[Jose Magalhaes]

An exhaust gas emission test might shed some light on the problem too.

Tony.

thanks. I'll see what they say on that one

 

[ge45ton]

I had emissions test failure on my early M44 but never had any warning lights at all, there was a code but can't remember what it was. I needed a new O2 sensor and then a while later a new Cat. I believe the later cars have two sensors in the exhaust for emissions, may be one of those? If you can I would take it to a specialist garage rather than BMW, these cars are quite old now and they don't always seem to have the experience with the Z3's.

 

[Jose Magalhaes]

I had emissions test failure on my early M44 but never had any warning lights at all, there was a code but can't remember what it was. I needed a new O2 sensor and then a while later a new Cat. I believe the later cars have two sensors in the exhaust for emissions, may be one of those? If you can I would take it to a specialist garage rather than BMW, these cars are quite old now and they don't always seem to have the experience with the Z3's.

Thanks. This next visit will be my last, that's for sure! And yes, I am leaning towards the O2 sensor and maybe the cat... I will need to find a good specialist