Rodge

Hi Guys,

My May 2007 E60 LCI 525i 3.0ltr N52 petrol engine has just failed the UK MOT emissions test.

Readings as follows:

1st Fast Idle Test - RPM 2250-2750 CO 0.01% (Pass) HC 21ppm (Pass) Lambda 2.14 (Fail)
2nd Fast Idle Test - RPM 2250-2750 CO 0.01% (Pass) HC 14ppm (Pass) Lambda 2.26 (Fail)

Limits - CO 0.30% HC 200ppm Lambda 0.97-1.03

The i-drive shows no reported faults.

I understand that one cause of high lambda might be air getting into the exhaust, although there are no obvious signs of leaks and the zorst is in good condition.

I believe high lambda indicates lean running, but there is no evidence of pinking from the engine under load.

So my questions are:

Is high lambda a threat to the engine (not that I'll be driving it until the test passes!) and has anyone had any experience of this problem which might read across and help me sort it?

My own research on the web tonight seems to show a worrying trend (by dealers of other marques) of an expensive willy-nilly exchange of sensors and zorst sections before the fault is finally cured.

Thanks in anticipation,

Rodge