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Nct fail question

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  • 10-01-2009 1:51pm
    #1
    Vain
    Registered Users Posts: 2,689 ✭✭✭


    Had my nct this morning for my mk4 1.4 golf and it failed on emissions. So anyway the guy told me its twice over the limit. This is what i failed on.

    Lambda: 1.032. Pass is between 0.97 and 1.03
    Co 0.45 vol% Above 0.3%. is a fail
    HC 374ppm Above 200ppm is a fail.

    Anyone know if its hard to get this sorted out and is it costly?

    Cheers.


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    #2
    Tipsy Mac
    Closed Accounts Posts: 2,559 ✭✭✭Tipsy Mac


    Has the car being doing lots of city driving at low speeds? Could be just a build up inside of pollutants, if you drive the bejaysus out of it at high revs before a restest that might fix it.


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    #3
    Darragh29
    Closed Accounts Posts: 7,097 ✭✭✭Darragh29


    Vain wrote: »
    Had my nct this morning for my mk4 1.4 golf and it failed on emissions. So anyway the guy told me its twice over the limit. This is what i failed on.

    Lambda: 1.032. Pass is between 0.97 and 1.03
    Co 0.45 vol% Above 0.3%. is a fail
    HC 374ppm Above 200ppm is a fail.

    Anyone know if its hard to get this sorted out and is it costly?

    Cheers.

    Was the engine very warm before the test was done??? This particular car can be tricky to get through the NCT emissions test if it is not just after being driven hard to the test centre! The lambda is just above limit, you might have a hole in your exhaust from corrosion that is the cause of this.

    On the HC which is 200% over limit and your CO, the problem is that the engine is running rich. This could be a lambda sensor problem, it could be caused by a vacuum leak causing excess air to enter the engine and the lambda sensor is detecting this excess air and adjusting your air:fuel ratio to compensate for the excess air, or it could be caused by a catalytic converter that has reached end of life. I found a similar problem before with a Mk 4 Golf was caused by the catalytic converter having been cut out of car car by a bor racer who thought the car would go faster without a cat and the car was sold to my customer who didn't know this had been done.

    This problem with emissions can also be caused by a defective temperature sensor.

    Best approach is to get the car hooked up to a diagnostic system and check the data coming from all engine sensors and also check for air leaks around the brake servo assist unit and vacuum hoses. Also check the cat for evidence that the matrix has come apart internally.

    Also, make sure before you do anything at all that the car is actually failing when the engine is hot. If this engine is cold or hasn't just come off a 10 mile journey, you will usually have trouble getting it past the NCT emissions test...


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    #4
    Steve
    Moderators, Category Moderators, Entertainment Moderators, Sports Moderators Posts: 22,584 CMod ✭✭✭✭Steve


    My GF's car had a similar fail a while back, it was caused by a small hole in the back box.


    Edit: it wasn't a golf, it was a pug 206.


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    #5
    Darragh29
    Closed Accounts Posts: 7,097 ✭✭✭Darragh29


    SteveC wrote: »
    My GF's car had a similar fail a while back, it was caused by a small hole in the back box.


    Edit: it wasn't a golf, it was a pug 206.

    This will cause the lambda to be above 1.03 and will cause the car to fail the NCT emissions for this particular parameter but it wouldn't be the cause of a HC or CO over limit fail as well, these are separate problems from a car that passes HC and CO but fails for Lambda. If a car just fails for excess lambda, this is almost always caused by a small hole somewhere in the exhaust tract downstream from the cat and lambda sensor, which was the case with your 206...


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    #6
    packas
    Closed Accounts Posts: 411 ✭✭packas


    MY Astra failed for CO2 emissions (high idle) only on Friday. All other readings were fine. The car was cold all day long in work car park. I drove to the test centre (2 km away). So gthe test was done with a cold engine. Does it sound like I just need to give the car a good run before the re-test?


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