NCT - FAQ

For safer, Cleaner motoring

The NCT was introduced on 4th January 2000. Ireland is one of the last countries to comply with the EU Directive, which makes car testing compulsory in EU member states and is aimed primarily at improving road safety and enhancing environmental protection. NCTS is operating this service on behalf of the Government and is committed to providing the highest standards of customer service

What are the emission levels my car needs to obtain to pass the NCT?

 

YEAR OF REGISTRATION

C.O. AT IDLING SPEED

H.C. AT IDLING SPEED  LAMBDA
BEFORE 1/10/86 > 4.5% > 1000 PPM  
FROM 1/10/86 TO 1993 > 3.5%  > 750 PPM  
1994 AND AFTER > 0.5%    
1994 AND AFTER AT 2500 R.P.M. > 0.3% > 200 PPM  1 + 0.03

What are the different gases my car is tested on? 

There are three different readings taken when your car is tested at the National car test centre. 

Carbon Monoxide (CO)
Carbon monoxide is a colourless, odourless, poisonous gas formed by incomplete combustion of petrol. This gas is emitted directly from the vehicle exhaust pipe. Incomplete combustion most commonly occurs at low air to fuel ratios in the engine. This means there is not enough air in the combustion chamber to burn all the fuel entering it. 

Hydrocarbons (H.C)
Hydrocarbon emissions result when fuel molecules in the engine do not burn or burn only partially. Hydrocarbons react in the presence of nitrogen oxides and sunlight to form ground-level ozone, a major component of smog. Ozone irritates the eyes, damages the lungs, and aggravates respiratory problems. It is our most widespread and intractable urban air pollution problem. A number of exhaust hydrocarbons are also toxic, with the potential to cause cancer.

Lambda
The lambda reading is not a gas but a ratio of air to fuel in the exhaust. An ideal lambda reading is 1. This means that all the fuel entering the combustion chamber is being burnt. In reality, cars are usually minutely rich or lean or varying between the two. This is the reason a variation of 0.03 is allowed on either side of the ideal ration of 1:1. A common misconception is that if your car fails the NCT on Lambda it means your oxygen (lambda) sensor in the exhaust is faulty. This may well be the case but it could also be the sign of an exhaust leak or another problem in the engine. We are fully equipped in McNamara's to test and rectify any of these faults.

Preparing for the NCT

Please prepare for the test by ensuring that:
1. Your car has adequate oil and water
2. The boot is empty and seats are clear of personal belongings such as removable baby seats
3. The vehicle is reasonably clean (especially the underbody)
4. The wheel hubcaps are removed and the tyres are inflated to the correct pressure
5. The timing belt has been replaced in the case of a diesel vehicle, i.e. within the timeframe specified by the vehicle manufacturer.

It is recommended that you co-incide the servicing of your vehicle with it's NCT.

During the servicing of your vehicle, we advise that you take special attention to (in order):
1. Headlights: alignment and condition
2. Brakes: front, rear and hand brake
3. Exhaust emissions: in most cases a slight tuning of the engine is sufficient.

Top Three Failure Items:

Year 2001 to date: the main failure items are Brakes, Front Suspension and Emissions. In the year 2000:

  • 43,000 pre 92 cars (1 in 6) were identified as having defective brakes.
  • 34,000 pre 92 cars (1 in 8) were over the emissions limit set by the European Union.
  • 32,000 pre 92 cars (1 in 9) had defective steering.

What can Mcnamara's do to get my car through the test?

Our workshop has the very latest test and diagnosis equipment to ensure the problem with your car is found quickly and repaired. We are also offer a same day service to fit catalytic converters and exhaust systems. Our stores hold an extremely comprehensive range of all parts related to petrol or injection systems on new and not so new cars. These include catalytic converters, oxygen sensors and the largest selection of carburettors and spare parts in Ireland.

 

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