Emmissions + MOT

AmDaMan

AmDaMan

AmDaMan

Soldato
Joined
18 Oct 2002
Posts
4,020
Location
Wellington, NZ
Right my car went for it's MOT and failed on some little things (headlights of of alignment, mudflaps too low etc)

Garage sorted these and changed the oild, filter plugs etc and it's still well over (like 7% i think he said) :(

What could be causing this?? Only thing I can thing i can think is running rich or a dodgy cataclyic converter maybe?

Luckily I don't have to pay for the 3rd retest but I'm sure the bills are already quite high now :(

Its a 10 year old 1.4 clio as many of you know!
 
Sorry I don't have an answer to your question, but on a pre-cat G reg car, is it still possible to fail on emissions?

Obviously, if it's blowing out thick nerve gas, I wouldn't be expecting a pass, but generally.
 
Amongst other things, could be the cat, could be the lambda sensor, or a leak in the exhaust. Also, have you changed the *air* filter? A clogged air filter can cause problems.

Also, if the car gets used for short trips, go out on an open road and let it warm up fully, then give it some stick for a few miles - can clear the throat of many a car :)
 
The filter is ok, I cleaned it before it bent it. The exhaust doesn't have a leak as i know of. What does a lambda sensor do? I use redex on it regularly too.

Mine also has a cat. Just don't understand why it was so much over!
 
The lambda sensor monitors the amount of oxygen present in the exhaust gas and alters the mixture of air and fuel entering the engine. If there is a leak before this sensor (for example in the manifold), it may be getting wrong readings. Or, the sensor may be faulty regardless - they do deteriorate over time.

Do you have the printout from the emmisions fail? If so, post the readings and we may be able to narrow down possible causes.
 
I havn't seen the sheet but the co2 was at 7% iirc so a considerable amount.

Where is the o2 sensor located?
 
If its running high CO (the limit is 0.3 IIRC?) then its probably running rich and not burning the fuel properly. Could indeed be the lambda sensor - but to be certain you'll need the whole sheet.

The lambda sensor is usually located on the downpipe after the manifold i.e. after where the exhaust branches out of the engine. Its easy to spot as its a thing that vaguely resembles a spark plug, screwed into the pipe, with a pair of cables running to it. Its easy enough to replace and shouldn't be expensive to buy, but I cant promise you 100% its that!
 
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