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Warning Emissions problem (NCT/MOT Failure)


I just had my car fail its NCT (Irish National Car Test, like the MOT).
It failed on exhaust emissions.
The readings were as follows;

Low Idle
(740 rpm)
CO: 0.18% Above 0.5% fails
HC: 0ppm Above 0ppm fails

High Idle
(2550 rpm)
Lambda 1.005 Between 0.97 and 1.03 Passes
CO: 1vol% Above 0.3% fails
HC: 56ppm Above 200ppm fails

I hope you can make sense of the readings.
Basically it failed on the High idle CO reading which was 1vol%.
What could be causing that ?
Could it be something as simple as the Air filter needs cleaning ?

I have to plead ignorance with these figures as they mean nothing to me, so any help would be appreciated.

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Re: Emissions problem (NCT/MOT Failure)

They make sense ...........i`m an MOT Tester

First thing to try is a good quality injector cleaner/ fuel treatment in the petrol.................This should clean all the crap out of the system

Then give it real thrashing and take it back to get it re-tested but keep it as hot as possible as the CAT works better the hotter it is

This usually does the trick
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Warning Re: Emissions problem (NCT/MOT Failure)

I have to agree with speedy, when I take mine for it's MOT I usually go for a 15 minute drive to get the cat good and hot then when I get to the test station get the emissions checked straight away.
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Thumbs Up Re: Emissions problem (NCT/MOT Failure)

I think I can give you good news! I have seen this type of reading a few times and mainly at this time of year. I think the car needs a good burn to get the cat to 'light up temperature' and it should go through no probs.

Another reason may be an inefficient cat- but I doubt it in this case.
Make sure that you use good quality engine oil with low ash content etc to prevent deposits on the monolith in the cat.

Your test station may well be only too happy to take your car out to get the cat hot, or they my be flexible enough to test it straight after you return from a roadtest.
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Re: Emissions problem (NCT/MOT Failure)

My old ship hit the same readings. My mechanic tried the booting it and checking it when hot but that was as near as he got.

I changed the air filter, cleaned out all the airways to the intake and bunged on a new Lambada probe, which made the biggest difference.

My new figures came in marginally better than the year before.

Ralf S.
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Re: Emissions problem (NCT/MOT Failure)

Is there a cheap and easy way to replace the lambda ?
What about the spark plugs. Could they be at fault ?
I have a BMC performance air filter. After cleaning it the last time I used WD40 to oil it. Was that a bad move ?


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emissions , failure , nct or mot , problem

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