emmissions and a rich lambda problem

[burtos]

i have a r reg clio maxim, and its been for its MOT recently, it failed on its emissions, CO and Lambda reading were way high, Lambda was changed and re MOT'ed the lambda and HC readings are now good but the CO level is still way high

first idle test
CO level - 0.82% 0 - 0.30 % pass

second fast idle test
CO Level - 1.20%

Natural idle test
CO Level - .99%

i have now taken the car to a Diagnostic garage, the engine management system has been checked, and they have said that the car passes on the first test but than fails on the next tests, the mechanic said that the lambda seems to be flicking\switching to rich and staying there and they are not sure why, as the report doesn't come back with any error messaging saying whats wrong.

1. First point is that does anyone have any suggestions as to why this may happen

 

[ditz]

what was the lambda reading on the emmisions data?

 

[burtos]

first idle test
lambda - 1.02 which is a pass

Second fast idle test
lambda - 1.02

 

[ditz]

slightly high if anything check for airleaks on the inlet side or exhaust if not check the lambda sensor