Failed Emissions MOT test

[nullogik]

I've suggested oil change because ages ago I've failed MOT as well. Bloke told me that if I've have fuel in oil (for whatever reason, can remember now - it was like 10 years ago) emissions are up by 1000...00 times Changing oil has sorted my problem and my car passed MOT.

(actually, it was in different part of Europe, but same idea)

Cheers
Chris

Thanks for that suggestion columb, but I think I can rule out dirty oil as the previous owner had the oil changed about two months before the failed MOT test.

 

[recycled]

Funny you should mention the Lambda readings recycled, I checked the MOT test documents this morning and the Lambda readings are as follows:

Car Reading 1: 0.83 (Test requirements, min = 0.97, max = 1.03)
Car Reading 2: 0.81

So it would seem that the Lambda sensor is too low. Consequently the car failed the Lambda test.

good. dieselman has given you the right ways. that lambda is trying to cover up for the air fuel ratio. it needs a tune up to sort out idling mixtures and ration. if you had a MAF it would have been easier done.
it is running rich .

 

[recycled]

Thanks Dieselman, I really appreciate your help on this matter

What is an AFR reading? I'm just guessing but does AFR stand for "air fuel ratio"? How might I get this reading?

I see from my Haynes manual that adjusting the richness is quite straightforward, I think there is a screw or Allen screw, than can be turned to adjust richness. Without equipment, is it possible to "do this by ear" i.e. listen to how the engine responds as I turn the screw?

yes you can try.
start it from cold and wait till the fast idle dies down, then adjust the screw until it is just about to hunt .
Not very accurate but it will help

 

[nullogik]

Just an update:

I found the mixture adjustment on the top of the breather and used an Allen key to adjust the richness. I did it in 45 degree increments anticlockwise (leaner) and now its 180 degrees from the original. As a result the car now seems to idle smoother and it starts without needing to give it some gas - just turn the key and it catches.

I don't know how my adjustment will affect the emissions as I don't have access to a gas analyser, but at least it will save me some fuel!

The idle still isn't perfect, but I discovered some corrosion on the back box and the pipe leading to it which I think once repaired will totally smooth out the idle.

Thanks guys for your help. I've loaded some pictures in the gallery of my Merc. The pictures aren't great, but I have some ideas for better photos once its been properly cleaned.

Pictures here: - more to come

http://www.mbclub.co.uk/forums/showthread.php?t=53494

 

[rajinder_1]

I have always found some Forte Gas treatment works wonders.

When you get it retested stick a can of that in the fuel, give it a good thraping to clear out the fuel system.

Its good to use an additive occasionally anyway so you dont loose anything in that respect and for a tenner its not alot of cash to part with.

Raj