Emissions failed on MOT but I went to a freindly garage!

My mechanic said it was running on 3, but I unplugged every coil pack and it dropped in revs everytime, so would suggest its not. It runs fine and pulls like a train!

Its the first MOT since owning the car - but the previous MOT emissions sheet says it was fine before.

What else could cause it to fail? The car still has the OEM cat.

Thanks

 

you could always do a rolling road session - should highlight any issues and very useful anyway

 

Buggered o2/lambda sensor mate, causing you to run rich, mine failed the same.

got mine from here Just Lambda, Suppliers of Bosch and NTK lambda sensors including zirconia and titania sensors by post..

 

i did replace it with a second hand one last year - but that could be shot i guess. And if its causing it to run rich - would I notice a difference in MPG? How else would I know its the lambda? wouldnt it run like a bag of nails?

 

Good idea - ive beem meaning to get it on one at some point. I guess if it is the o2, then that would diagnose the problem....

 

Only way i knew the lambda had gone was because my AFR meter stopped cycling, and mpg was prob down but nothing really noticable.
You could always test it with a multimeter