Lambda position, emissions etc

[Colesy]

The MOT is due and I thought I'd fit a new Lambda sensor I've had on the shelf for a while. Last year the emissions were very hard to pass and I was wondering whether it might be due to a duff sensor or it could be a problem with my downpipe. I always thought that the mounts for the lambda looked very deep, so I was wondering if they could be an issue at all?

Another side issue is that the sensor sticks out and catches on the airbox on removal so I was wondering if using the hole further away from the turbo would be an issue?



Cheers for any help.

[UrS4boy]

Both of those bungs look very (too) tall. This would prevent you from getting the tip of the G39 O2/Lambda sensor into the exhaust flow. I guess all you can do is try the sensor in the shorter bung.

G39 info: http://forums.quattroworld.com/s4s6/msgs/21012.phtml

Stock:

[twoqu]

Have you experienced the infamous 00561 mixture adaption code with that set up?

[Colesy]

No, all codes have been clear. The mounts are threaded all the way down so I might look into cutting them shorter if the emissions are still tight.

[Colesy]

Passed the MOT! Although a less generous tester might have failed me...

The Co2 reading is my problem, got it very hot today and still the best reading I saw was 0.35 and that was only for a second the average on fast idle was ~0.6...

Would ideally like to get this sorted in time for next years MOT, is CAT cleaner worth getting? Or would shortening the bung be the best place to start? Any other suggestions?

[diesel des]

Shorten the bung. But your cat sounds tired. Was lambda close to 1.

[Colesy]

Shorten the bung. But your cat sounds tired. Was lambda close to 1.

I'm not sure of the exact lambda value, it was well within the limit though. I had the cat off a few weeks ago and it was structurally in perfect condition. I did used to use a lot of oil before cleaning the breather system out so could the cat still be caked up from this?

[diesel des]

If lambda is 1 and your co is high you cat is knackered. The oil could of killed it.

[SteveH]

Those O2 bungs look too long for the standard lambda sensor. I'd cut one down and get the sensor right into the flow if possible.

[sjw185]

My downpipe is a similar setup to yours though the bung nearest the turbo is in the wrong place as the lambda probe hits the airbox.
I am using the bung futher down the pipe cut down to get the lambda in the flow but I get the infamous 00561 code as well