High Lambda reading on Exhaust gas tester

[omeydz]

Hi.

Had a pre-MOT test and the lambda readout was 1.27 and pass is 1.03.

This is with a thoroughly warm engine and ECU map is stock VW map.

Its a code CAXA 1.4 TSI 122bhp engine.

Any ideas what could have caused this? 

Last year it scraped a pass after 3rd or 4th go on the analyser, again with warm engine and stock map.

Been told by master tech mate it could be the cat, lambda sensor, or leak in the exhaust/intake..

Intake is new and exhaust has been apart recently and sealed up on refit and leak-free so can discount these. No engine management lights. Recently did fuel treatment BG44K few tanks of fuel ago if that makes any difference?

Any help much appreciated

[pudding]

Was that the CO2 reading at idle?  If so, that's massively high.  Should be well under 1!

Lambda faults would definitely throw up an engine management light.  Has it been fault coded and have you looked at the idle and part throttle long term fuel trim measuring blocks?

[Dan_FR]

1.03 limit is the Lambda/AFR - a pass is 0.97 to 1.03 from memory.

 1.27 is massively lean. Check what the cars lambda sensor is reading as it could be duff.

[omeydz]

CO readouts were normal. Its lambda thats too high.

Thanks will check tomorrow!