Emissions issue

[DrSheila]

Hello everyone, my 1998 Z3 1.9 has just failed its MOT because of over high emissions. A lambda sensor replacement solved one part of the problem but despite changing the spark plugs and flushing the engine out whilst ticking it over for a couple of hours the emissions were still too high.
The ‘German car expert’ garage it was in didn’t seem to have any more solutions and I removed my car with a failed MOT and £290 lighter for other stuff carried out on the car.
Does anyone know what might be the cause of higher emissions in a Z3 and what the solution might be? Any advice welcome

 

[t-tony]

First we need to see a picture of the emissions failure to see which gasses it failed on and at what level.

Tony.

 

[colb]

Some diagnostics required, check the fuel trims in live data to see what they are doing, a rich mixture caused by air leaks making the car see a lean mixture will cause it to add fuel at the injectors, if this continues it should set an engine management light to draw attention to the fault emmissions would be elevated because of the overfueling. Another cause could be the Cat not functioning correctly, that would require a new Cat being fitted.