Help with emissions for nct

topspin57755

hey iv had an issue with extremely odd emissions for my nct
low idle
CO 0.31 (above 0.30) fail
HC 146
High idle
Lambda 0.93 (not between 0.97 and 1.03) fail
CO 1.85 ( above .20) fail
HC 607 (above 200 ppm) fail
everything else passed on my test, my test was at 22:10 and i got in my car at 21:30 as i don't live far could a cold car have a impact also what can i do to pass the next time?

Leonard Hofstadter

What car is it (make, model, engine and year)? Are there any warning lights on the dashboard?

Yes, a cold engine could fail an NCT - but I suspect you've got other issues to contend with as well, since some of those emissions readings are well above the acceptable limit.

topspin57755

captainspeed wrote: »

What car is it (make, model, engine and year)? Are there any warning lights on the dashboard?

Yes, a cold engine could fail an NCT - but I suspect you've got other issues to contend with as well as some of those emissions readings are well above the acceptable limit.

I drive a 2006 VW golf 1.4 only have 155,000 km

Leonard Hofstadter

It could be a faulty sensor (not all engine related faults will cause a light to come on - although an emissions related one most certainly should), that is affecting the air/fuel ratio and that is causing it to fail.

My hunch though is that even if the lambda (air/fuel ratio) was 1 (the optimum value) the car still wouldn't pass, although it would help an awful lot.

Another possibility is the catalytic converter - but that would require fixing the air/fuel ratio first, as there is no point in changing one with a rich running engine, you'll just burn it out and have to change it a second time.

However, those engines have a reputation for burning oil, and they can burn lots of it. Depending on oil usage that can be quite a problem for passing an emissions test. It's normally considered acceptable for a car to burn a litre of oil every 600 miles / 1000 km, but if it's quite a bit more than this then it's going to put the emissions right out.

The truth is, you'd need a competent mechanic to look at it, internet speculation on my part is merely speculation.

Bmw123d

I reckon it could be the breather pipes.

bonky2018

I alway run engine take a car for hard burn in low gears down a motorway day before a NCT to blow any excess out the system
The two hours before NCT start engine and let it idle for one hour to get engine hott but mostly to ensure the CAT get roasty hot
Then i drive to NCT in lowwwest gears highest RPM to make engine and CAT real extra hot .
Then when i arrive i have both sets of key leave engine running go in hnd in one set of keys return to car and keep engine running .
When i see the NCT tester come out to take my car I switch off engine take keys away and let NCT tester take car.If it is very early day booking like 8am they often test car straight away and its all toasty hot.If it rush hour the car might sit half an hour cooling off before testing but is still a lot hotter than most cars

This trick works for most cars that failed the emmissions forst time around where the numbers wer just over the limits

In your case i suspect it wont work

Then your into doing other things like special fuels in carberator trick or repairing the faulty sensor but if its oil burning problem that has gummed up the CAT your maybe looking at new cat to solve this .If you have to get new cat then when the car passes the NCT emmision remove the new CAT and put back the old CAT.Then the next year put the new cat on to pass the Emmisisons and swop it out again when you passed the NCT. The reson for this is a CAT is not able to burn engine oil and gumms up so you would risk to have have to buy a new CAT every year to pass NCT tests every year.
youtube video on how a CAT works explains the system . Washing out gummed up CAT doesnt appear to work to solve the problem of CAT which is gummmed up

Bmw123d

bonky2018 wrote: »

I alway run engine take a car for hard burn in low gears down a motorway day before a NCT to blow any excess out the system
The two hours before NCT start engine and let it idle for one hour to get engine hott but mostly to ensure the CAT get roasty hot
Then i drive to NCT in lowwwest gears highest RPM to make engine and CAT real extra hot .
Then when i arrive i have both sets of key leave engine running go in hnd in one set of keys return to car and keep engine running .
When i see the NCT tester come out to take my car I switch off engine take keys away and let NCT tester take car.If it is very early day booking like 8am they often test car straight away and its all toasty hot.If it rush hour the car might sit half an hour cooling off before testing but is still a lot hotter than most cars

This trick works for most cars that failed the emmissions forst time around where the numbers wer just over the limits

In your case i suspect it wont work

Then your into doing other things like special fuels in carberator trick or repairing the faulty sensor but if its oil burning problem that has gummed up the CAT your maybe looking at new cat to solve this .If you have to get new cat then when the car passes the NCT emmision remove the new CAT and put back the old CAT.Then the next year put the new cat on to pass the Emmisisons and swop it out again when you passed the NCT. The reson for this is a CAT is not able to burn engine oil and gumms up so you would risk to have have to buy a new CAT every year to pass NCT tests every year.
youtube video on how a CAT works explains the system . Washing out gummed up CAT doesnt appear to work to solve the problem of CAT which is gummmed up

U souldnt leave the car idle for long at all this is ur problem it fills the exhaust with smoke. If you leave it idle u must bring it for a good spin. Not leave it idle outside the nct

Gary Gleeson

In the past, my mum's car had high emissions and the mechanic advised us to take it for a spin down the motorway. So I did, putting my foot down intermittently to clean the exhaust out and when the car went for the retest it passed.

Now, I can't remember how high the emissions were, but before every NCT test I always take it for a spin to clean it out and it sails through every time.

I am not a mechanic and I am just saying what works for me. It's hard to diagnose what the reason behind your high emissions is, so you are always best to get your mechanic to look at.

Regards

Gary

mullingar

It's running Way too rich, so either it's too much fuel or not enough air is getting in so their is not enough oxygen to burn with the excess fuel hence high CO and not fully CO2 and unburnt HC (hydrocarbons)

section4

My car, a mazda 6 1.8 petrol failed on emmissions today.

Co 1.15% above 30 fail

Hc 350ppm above 0 n\a

LLambada 0.89 between 97 103 fail

co 3.78% above 0.20% fail

Hc 126 above 200rpm pass

Can anybody make any sense of this in terms of rectify it thx