1993 W124 220TE (M111) Mot Emissions Fail Help

[tjamesbo]

Any experts on diagnosing Emissions Problems I scraped through the MOT last year but despite Injector cleaner / Cataclean / OIl Change / Clean Air Filter / MAF cleaned with MAF cleaner / Coolant temperature sensor resistance checked / and a high speed italian tune up on the way and using Dipetane at the MOT it sadly failed as below. The Car drives Well / Idles well / Plugs look OK so I’m looking at the 16 pin diagnostic ( see my other post ) and then possibly checking the o2 lambda sensor voltages and maybe the MAF voltages if I can find the spec values and possibly thinking air leak? or cat has failed?
Any guidance appreciated

 

[joderest]

Not an expert, but would not an air leak make the mixture lean ?? not rich.
On my old ML270 fitting an oil catch can in the pipe between rocker cover and turbo reduced the readings.

 

[LostKiwi]

Replied on your other thread Boyd, but yes my gut feel would be Lambda or cat, especially as there is no feedback system on the cat to tell the ECU it's bad.

How old is the catalytic converter and lambda sensor?

 

[tjamesbo]

Hi LK yes not many miles done really on the cat and lambda they were changed when the car was resurrected about 4-5 years ago but only about 10K miles or so ago but the cat was a REACT from GSF so a cheapie , the lambda was also renewed at the time . I'm trying to avoid the replace this then this and still have the problem scenario guess my only option is to eliminate each component step by step and the lambda isnt an expensive part . I do wonder if there is a small air leak somewhere as well and I have bought a catch can as when i looked at the breather between the cam cover and the throttle body it was quite oily so that wouldnt be doing much good guess its just work through some cheap options and drop it in just for an emissions and if its right wang it in for a quick Retest alternatively someone has suggested 15-20% acetone or ethanol carb cleaner in the fuel just for the test that gives me the summer to sort it properly as I could do with it as my preferred daily at the moment as the vito has a swirl flap issue on its OM642 and aircon which needs sorting before any hot weather , and i havent commissioned the 320TE for the summer yet so I'm 3 down out of Five at the moment trying to survive with just 2 cars

 

[LostKiwi]

An air leak is a possibility though I'd expect that to make it run lean as the MAF will see less air so add less fuel.