Fast idle test

[Rathcon]

Hi all,
After a bit of advice regarding a fast idle test failure for the lambda reading.

First test results:
CO 0%
HC 8ppm
Lambda 1.20

Second test:
CO 0%
HC 2ppm
Lambda 1.38

Lambda limits 0.97 - 1.03

Can anyone give some help regarding where the cause of the failure could be?

Thanks!!

[LandieMark]

Exhaust or manifold leak prior to the sensor or bad sensor. It's basically running too lean according to those figures.

Beyond that, is the limit of my knowledge.

[mintmansam]

Exhaust leak, it could be drawing air in this causing the high lambda

From the other results seems like the car is running well

I have it with my car , I had to replace the rear section of the exhaust

[Rathcon]

Thanks for that, much appreciated. Will have a look for holes!!

[stevemcs]

What car and any advisories for exhaust ?

[Kuwahara]

Could be a pinhole size and fail on the lambda,out of interest what model is it…

[Rathcon]

VW Up, not mine so will ask if there was anything mentioned about the exhaust.

[GreenV8S]

According to the CO readings, it isn't running rich. It might be running lean. It might just have an exhaust leak upstream of the ECO sensor causing an artificially high lambda reading. In some situations this would cause the ECU to add enrichment, causing excessive CO and HC readings. Presumably that isn't happening here since the CO and HC readings are healthy.

[stevemcs]

We had one that struggled a few weeks ago, although it was struggling on co. Pretty sure that was a temp sensor causing it to run rich.

The up is usually pretty good when it comes to emissions

[stevieturbo]

It screams exhaust leak

[E-bmw]

^^^^ As others more qualified than me have said high lambda = oxygen where there shouldn't be any = exhaust leak.

[Rathcon]

Thanks for the replies, there is also a comment for an exhaust leak on the paperwork so that'll be it then!!

Thanks again

[TwinKam]

stevieturbo said:

It screams exhaust leak

...and it will be DOWNSTREAM of the sensors, ie towards the rear of the car, likely the rear silencer.

[tux850]

TwinKam said:

...and it will be DOWNSTREAM of the sensors, ie towards the rear of the car, likely the rear silencer.

Although failed flexi sections are common.

(Edit: To clarify; so downstream but not at the rear end!)