Lambda Probe

[Sidspud]

OK - please excuse my ignorance, but what the hell is a lambda probe?

What does it do? I'm getting bloody awful fuel economy and everything I read points to changing this part. I'm all for changing it, but I don't know what it is, what it does, or even what it looks like.

Any help would be greatly appreciated.

[porkkis]

It measures the amount of oxygen in exhaust gases and using that info the ECU can determine the mixture that engine is running on. Faulty sensor might give false values and therefore ECU enrichens (or makes it leaner) the mixture thinking it should do so.
The lambda value is not used always. Typically only in "closed loop" ie not on wide open throttle. I think on s2 ECUs there are other rules also, boost, rpm etc. Mihnea or Paul could probably tell when lambda is used and when not.

[Stick Insect]

The Lambda probe is an electronic sensor which is positioned in the exhaust manifold ( ahead of the cat ). It monitors the gasses flowing past for unburnt hydrocarbons etc. this is fed back to the ECU which then adjusts the mixture etc. They can be damaged by certain exhaust emissions. Ford Zetec engines if the oil level is too high can damage their Lamda probes and their catalytic converters.

Here is a photo of one which is covered with a carbon build up.

http://www.aew69.dial.pipex.com/pages/Carboned%20Lambda%20Probe.htm

If you have an oily turbo then this can mask the probe and stop it working properly.

I think new ones are about £60

I hope this was of help.

[Dr H]

Check out this guide on Mike's site:

http://www.s2-audi.co.uk/tech_articles/lambda_sensor_replace.htm

Mine cost £65 + VAT for an original probe from those lovely guys at Vagparts

HTH

Leigh

[Glen Chamberlain]

I paid £45 + VAT from a local BOSCH supplier! Pretty good i thought! Parts numbers are exactly the same as OE!

[horvathg]

Exactly, what do you recognize or measure when your lambda probe exchange was done and it cured your problem? Should fuel consumption go down a bit or should some measurable changes occur or how do we convince ourselves that the probe was faulty? It is very important please guys.


Gabor

[dan_b]

What symptoms does a faulty/old lambda probe give to the S2 driving experience? As Horvag said, how do we recognize that our lambda needs replacing, other than just randomly deciding it needs to be done and doing it.

It seems like a simple enough job according to Mike's guide.

What's the part number? Is the Bosch one exactly the same as the Vagparts one?

[Mikes2]

Higher than expected fuel consumption and possibly rough running with hesitant acceleration although this is rare.

Replacing it usually results in a smoother idle and crisper performance with improved mpg.

The Bosch part number is on my site somewhere

[dan_b]

Thanks Mike, I think this sounds like what I need to do (along with the 'stat!), I'll check out your site - your guide to replacing the lambda is helpful!

[Mikes2]

Access is improved if you remove the airbox cover. Just watch your fingers on the clips