NCT Failure

msdurden

My car failed the NCT today becasue I had 'high emissions'.

I haven't a clue what that means, any ideas?

peasant

It means your car is a "stinker"

could have several reasons:
- it needs a "tune up"
- you've got a hole in the exhaust
- your lambda sensor is malfunctioning
- your cat has desintegrated
- many, many other possible reasons, depending on the type of car/engine (including bot not necessarily ...engine exitus)

Get it to a good garage to check it out.

mike65

It proberly means your catalytic converter is dead but it could be something else like a poorly adjusted air-fuel mix/failed o2 sensor, they should have said or the paperwork should tell you.

Mike.

kikel

Just drive to the retest in 3rd gear or drive hard. Believe it or not it works. Sometimes

astraboy

Same thing happened with mine recently. THe report should say if its the lamba sensor, or something else. If it is the lamba, its about 100 euro for a new one and should solve the issue straight away. If not, maybe the sensor is getting the wrong reading due to a hole in the exhaust or manifold, or maybe your cat is busted. Also, your engine may just need to be adjusted for fueling or have the injectors cleaned. What kind of car is it? Post up what the report says you failed on and we could point you in the right direction.n

michaelanthony

Pour in 2 bottles of petrol treatment into a quarter of a tank of petrol and drive the bollocks out of the car before the test so the engine and cat are nice and hot to minimise the emissions.

JHMEG

And don't forget to drive the stones out of it... it fixes all sorts of things, like tracking, holes in exhausts etc :rolleyes:

Diesel or petrol?

Read the test report. What emissions are high? HC, CO or Lamda? They're all caused by different things...

Capt'n Midnight

Like the fella said read the report.

it will state the limits and what your car reached. if you are close to the limits it may not be such a problem, but if you are miles away

gobby

Did it fail on idle or when reving?

Darragh29

Can you post the emissions data on the sheet that the NCT gave you up here???

Darragh29

astraboy wrote:

Same thing happened with mine recently. THe report should say if its the lamba sensor, or something else. If it is the lamba, its about 100 euro for a new one and should solve the issue straight away. If not, maybe the sensor is getting the wrong reading due to a hole in the exhaust or manifold, or maybe your cat is busted. Also, your engine may just need to be adjusted for fueling or have the injectors cleaned. What kind of car is it? Post up what the report says you failed on and we could point you in the right direction.n

The report will give a lambda value but will not point to a device that is causing the problem such as the lambda sensor.

JHMEG

Darragh29 wrote:

Can you post the emissions data on the sheet that the NCT gave you up here???

I guess not. Maybe he/she has forgotten about it...:rolleyes:

thatshandy

My car failed today for exaust emmisions also. it a 99 opel astra. Passed everything else. Failed in High idle it read CO 0.62 vol % above 0.3 is a fail.
Also HC read 198 200 & above is a fail so it just scraped it ther. What causing this does anyone know. And more importantly how do you fix it!!!:(

Darragh29

thatshandy wrote:

My car failed today for exaust emmisions also. it a 99 opel astra. Passed everything else. Failed in High idle it read CO 0.62 vol % above 0.3 is a fail.
Also HC read 198 200 & above is a fail so it just scraped it ther. What causing this does anyone know. And more importantly how do you fix it!!!:(

I just had a car in failing the same thing except HC was 209 PPM, just above the limit and CO was 0.64, roughly twice the limit. It turned out that this car I had in here had the catalytic converter removed and a pipe put in instead. Fitting a catalytic converter has fixed the problem in this case. You would need a mechanic to look at it for a proper diagnosis, but I imagine your catalytic converter could be worn, particularly if CO is failing. One of the functions of the catalytic converter is to chemically recombine two molecules of Carbon Monoxoide gas (2CO), with an O2 molecule and the result is a harmless gas, CO2. Another function of the catalytic converter is to juggle with unburnt HC's to cause HC's to recombine with other gases to result in H2O (water) and CO2 (relatively harmless Carbon Dioxide).

If you have a high HC emissions reading, this means that you have unburnt HC's (Hydrocarbons, also known as "petrol"), passing through your engine and leaving via the exhaust pipe. The idea of the lambda/oxygen sensor is to constantly mix the air:fuel mix so that you have the ideal air:fuel ratio in your engine which is 14.7 parts of air to 1 part of petrol.

However, if you have a high HC reading, this could be due to an engine oil excess consumption problem. Engine oil is also a Hydrocarbon, and if your engine is burning excess oil due to engine wear or leaking valve stem seals, etc, your excess HC reading could be due to this.

In the case of the high HC reading, your car is burning too much fuel or is not fully burning the fuel charge that is delivered for the following reasons:

(1) The combustion of fuel taking place within the chamber is poor, you might improve the combustion by replacing spark plugs. You could have a problem with a HT lead or a distributor that could cause the same effect.

(2) You might have worn piston rings/oil seals, worn valve stem oil seals, dirty throttle body causing poor ignition, or somehow, excess engine oil ending up inside the combustion chamber burning with fuel.

(3) Too much fuel is being loaded into the combustion chamber, possibly caused by a faulty lambda sensor.

(4) Your catalytic converter is not dealing with the HC's it is getting as it is worn.

A few questions...

(A) Is there any white smoke from the exhaust when you rev the car that looks a bit unusual?

(B) Is the engine idle RPM stable? When you are sitting in the car with the engine running, is the RPM relatively stable at 750-800 RPM or is it going up and down?

(C) Do you hear a noise from the exhaust like loads of bits of loose metal floating around in your exhaust pipe?

(D) What is the lambda value for the emissions test at high idle? It should be between 0.97 and 1.03 if you have passed this part of the test.

As you have a high HC and also a high CO problem, this points to the catalytic converter being the issue, but you need to eliminate simple things first like bad ignition which could be caused by dirty/worn spark plugs or also excessive engine oil consumption.

Just based on my own recent experience, just check that some boy racer muppet hasn't removed the catalytic converter and replaced it with a straight pipe!