MOT emissions test

[ocrp]

I have been looking at the MOT emissions tests for the last two test on my car (Passat '99 1.8 SE).

The limits for the Lambda are 0.97 - 1.03. Last year it recorded 1.01 and this year at 1.03.

Is this indicating a problem with the sensor or maybe something else, and will it be likely to fail next years test?

I'm a bit clueless in this area so any help would be appreciated.

[Mook]

It won't be the sensor on your car, it'll be the catalytic convertor. The Lambda probes measure the amount of nasty stuff the cat is letting through - hence the increase in the reading. The readings used in the test are from the probe that's put into the exhuast during the test (and this has to be checked at least once a year for accuracy).

It's very, very difficult to tell whether it'll fail next year, but going on the increase to this year where it's on the limit, it's quite likely it will. IIRC, you can get replacement non VW cats for about £500. A fair chunk on money, I know, but probably worth spending the money if it's a reliable car and does the job.

HTH

[Tobes49]

[ QUOTE ]

It won't be the sensor on your car, it'll be the catalytic convertor. The Lambda probes measure the amount of nasty stuff the cat is letting through - hence the increase in the reading. The readings used in the test are from the probe that's put into the exhuast during the test (and this has to be checked at least once a year for accuracy).

It's very, very difficult to tell whether it'll fail next year, but going on the increase to this year where it's on the limit, it's quite likely it will. IIRC, you can get replacement non VW cats for about £500. A fair chunk on money, I know, but probably worth spending the money if it's a reliable car and does the job.

HTH

[/ QUOTE ]

Not quite, A lambda sensor measures the amount of Oxygen in the exhaust gas, A lambda of 1 is equal to 14.7parts of air to 1 part of fuel this is called a stoichiometric mixture. A higher lambda means there more parts of air in the exhaust system. Can be caused by a lot of things (inc a hole in the exhaust before the lamda probe.

£500 will buy you a geunine cat and £150+will buy you a pattern part.

[ocrp]

Thanks to both of you. It could very well be a hole in the exhaust as I have had for a long time now, a very raspy exhuast sound from the front underneath of the car. Have been meaning to get it checked out, but you know how these things are.