Hi

I have a 1.2 12v polo 2002 which has just failed its MOT on emissions. This is our holiday car in Cyprus and we are back in UK now - this makes sorting the problem out a bit more fun!!

Emission readings were:

CO2 0.20

HC 15%

Lambda 1.142

Whilst there I had a new No1 Lambda sensor fitted, after this the Lambda and HC readings were ok but the CO2 went up to 0.60!

Anyone else had this problem? is this likely to also need the bottom Lambda or has my cat most likely gone? Someone did tell me that with changing Lambda 1 that the bottom one could be pulsing?

Any help much appreciated as I am most likely going to have to take parts over in my luggage

Cheers

Paul

There is a common problem with some cars where the first sensor shows a problem but its actually the second sensor to blame, but I'm not sure if VWs suffer from this.

Carrying a catalyst in your luggage might be a fast way to a lengthy explanation to the airport police.

A packed lambda sensor probably look pretty dodgy on x-ray. Lol

Go back with a nissan micra and slip the tester £20.

Go back with a nissan micra and slip the tester £20.

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DON'T GIVE OUT DUFF ADVICE. IF YOU DON'T KNOW THE ANSWER THEN DON'T ANSWER - SIMPLE!!!

Why did you have the lambda sensor change was it plugged in and code read.

Could be a few things could be the other sensor like already said could be a temp sensor these a pretty common. Could just need a service and clean the throttle body out.

If its has not been running well for long while the cat could be gone but would be the last thing I would do as they only get damaged when fuel goes through the (misfire)

Try and get the codes read if not around done

Agree with above. First get codes read if there are any (is there a DTC/check engine light present?). If the CAT had failed, the second lambda sensor would have noticed this (that's what it's there for) and thrown a warning up (assuming it's just the CAT that has failed).

I'd also say that the car really needs to be hot to pass, the CAT doesn't do it's job properly until it's stonking, and I think the second lambda ignores readings from the CAT until a set time period when it knows the CAT will be hot enough to actually change the gases going through it. So if you are getting it emissions tested before the CAT is hot and working, the emissions tester will tell you the car isn't running as it should, when really there isn't a problem.

To clarify, did you mean to state CO (carbon monoxide) content, or CO2 (carbon dioxide) content?

Were these failures at idle speed, or fast idle (>2000rpm)?

And to shed some light on your first test results (before the lambda sensor was changed), a high lambda value (>1.03) can indicate a leak in the exhaust somewhere between the last lambda sensor and the emission tester nozzle. Was anything like this also mentioned in your MOT, a blowing exhaust?

"Lambda" refers to the oxygen content (as a ratio) in the gas coming out, so high lambda means too much oxygen. In my experience, if a lambda sensor stops working, the car usually runs rich, which would be indicated by a lower oxygen content, hence low lambda reading (<0.97) and usually also with a high CO content (>0.30 - fail).

Edited 21 August, 201313 yr by CWA

Thanks for all the replies.

It was the CO not CO2 reading. The test was done at 3 speeds, the print out we have shows engine speed 2890 - not sure which this one was. They didn't mention any leaks on exhaust however, the only problem we had with the MOT test station was the language barrier - Greek/English. We changed the Lambda 1 sensor because the MOT failure notice said upper Lambda which did resolve the lambda reading but threw out the CO reading

There are no warning lights on.

The car does spend 3 months at a time parked up. At the time we had the MOT done it was 35-40 degree heat during the day and the car was hot!

Have seen some diagnostic machines on ebay, anybody got any ideas on which would be the best and if worth getting to take with us on next trip?

Cheers

Paul

Buy this as the cheapest option, it should do the job - http://www.ebay.co.uk/itm/VAG-GROUP-USB-CO...=item3f1b0d351a

It's for Volkswagen/Audi/VAG cars only though. You can download VCDS-Lite software online. You can get other more expensive code readers that may be used on other cars if you want to use it on a car from another manufacture.

There will probably be old codes from before the sensor was replaced, make sure you clear them then run the car again for the new/still relevant codes to pop up again.

Hmm, maybe it was the lambda sensor.. I've also heard that it takes a while for new sensors to calibrate, or "adapt" themselves (not 100% on this). I'm not sure how long this process takes though, whether it can be done in a 5/10 minute drive around the block? Plus, I would have thought/hoped that the garage would know about this if it's the case.

Is there any update on it fella?

Go back with a nissan micra and slip the tester £20.

Not useful or constructive, consider yourself warned

DON'T GIVE OUT DUFF ADVICE. IF YOU DON'T KNOW THE ANSWER THEN DON'T ANSWER - SIMPLE!!!

What happened Ceri ? You used to be cool.

Go back with a nissan micra and slip the tester £20.

Not useful or constructive, consider yourself warned

DON'T GIVE OUT DUFF ADVICE. IF YOU DON'T KNOW THE ANSWER THEN DON'T ANSWER - SIMPLE!!!

What happened Ceri ? You used to be cool.

Its Spain, you'd just have to take some beers and get your missus to flash her chebs!

A duff cat isnt the end of the world and saves spending a load of cash on parts to have them crushed by some customs cleft looking for class a's, you mind find then want a piece of your chocolate starfish.

Anyway whats the limits for the mot test in spain? Is the garage reputable and do they work on vw's namely of that age? If they dont have a code reader, then they arent worth using.

In these hard times, i know what option id be picking re: a fix!