MOT Fail

11th January 2011, 17:37

My car went in for its MOT today and by some sort of miracle it only failed on emissions. The mechanic at the garage put some additive through it but its still just failing.

Now he says that im probably best off changing the lambda sensor and the pipe it connects to, (cause the current one has a rusted sensor attached to it and it wont come off lol),

Do you reckon this is the best idea? I have had the car for nearly a year and dont really know much about its past. Plus what kind of price do you think the its going to cost me, unfortunately I've got to pay a garage to do it as I havnt got the time to do it before i go back to uni with work.

12th January 2011, 10:10

READ:

The exhaust gas oxygen sensor (EGO or O2), or lambda sensor, is the key sensor in the engine fuel control feedback loop. The computer uses the O2 sensor’s input to balance the fuel mixture, leaning the mixture when the sensor reads rich and enriching the mixture when the sensor reads lean.

Lambda sensors produce a voltage signal that recognises the amount of unburnt oxygen in the exhaust. An oxygen sensor is essentially a battery that generates its own voltage. When hot (at least 250 °C), the zirconium dioxide element in the sensor’s tip produces a voltage that varies according to the amount of oxygen in the exhaust compared to the ambient oxygen level in the outside air. The greater the difference, the higher the sensor’s output voltage.

Shop around for a couple of quotes, there is NO obligation for the garage that carried out your MOT to have to do the work?

12th January 2011, 11:04

Which lambda sensor does the garage recommend changing? I believe there are two, 1 in the manifold and 1 further downstream (I'd assume that it'll be the first one).

I have the same problem on my VTS - New CAT's been ordered but not convinced that's the problem.