Failed NCT on emissions

GiuliaM

Hello all, I know nothing about cars so I was wondering if anyone has suggestions for me.

I failed my NCT for emissions and tyres. I have a 2007 petrol Polo. the values were high in CO low idle e CO high idle. the lambda was ok. The mechanic replaced tyres, changed oil filter, changed oil, and sparks plugs. He couldn't test the emissions but said it would be fine for the retest. It wasn't and I failed the NCT again. this time only on emissions, and only on CO on High Idle. The value is 0.41% and shouldn't be above 0.20%. now, I am kind of desperate because I live in Sligo and called so many mechanics but half don't have the emission tester and others are fully booked until the very last day I have to retest it. Some told me I should put a new cat and lambda , even if lambda value is fine (its 1, and the range is between 0.97 and 1.03), and told me prices like 600 euros for cat and lambda. some suggested to use dipetane. I bought a bottle and was thinking to try another test after using that at this point, since if i have to bring the car to a mechanic i will have to take a new full test anyway because it would be too late for a re test. Do you have suggestions on what could be the issue? might be enough the dipetane? I read on another thread that if the CO is high on high idle its definetly a cat problem and dipetane won't work.

I can't buy another car because I plan to leave the country next year, so it would be just for other 6 months that i need the car roughly.

thanks all!!

Calahonda52

what mileage?

hoodie6029

Are you giving the car a good long drive (20 or 30 mins) before the test? Bring a car with a cold exhaust can caused high emissions figures.

I’d put the dipetane in, drive it everyday for a few days, so it can work it’s way through the system. Bring the car to centre after a decent drive. It’ll cost you more than €28 at a garage to find out whether it’ll pass or not with no guarantee, so you’re better off just bring it back to the NCT.

Best of luck!

GiuliaM

https://www.boards.ie/discussion/comment/121025596#Comment_121025596

96000 miles

GiuliaM

https://www.boards.ie/discussion/comment/121025674#Comment_121025674

I did try to give it a 15-20min drive last time, being on high revs for a while on third gear, but then i had to wait half an hour for the test (they were late on the schedule). the guy at the nct center tried for a long time to make the value low, but I think he can't stay too much on a car. the engine temperature was 83 degrees.

thanks for the advice!

User1998

Servicing the engine was never going to be enough to make it pass.

€600 is way too much for a catalytic converter. You should only be paying €250 or so.

Try get a new catalytic converter fitted for a reasonable price and if that doesn’t work then theres probably not much else you can do other than replace the engine.

Sometimes when these old Polos fail on emissions it can be impossible to make them pass. And if it does pass you’ll probably have to replace the catalytic converter again next year.

CoBo55

Is it using oil? They're an absolute dog of an engine, practically impossible to get through emissions once they start failing, a new universal cat might squeeze it though and give you the few months you need, best of luck👍. A compression test would be where I would start, it could have a burnt valve.

GiuliaM

No it's not using much oil. Should I try another retest only with dipetane while i wait for the mechanic appointment or it would be wasted money?

User1998

Waste of money. It needs a catalytic converter. Even that may not get it to pass.

GiuliaM

yes, they said 600 between cat and lambda. they robbed me other times and it was my last option to call them to see if they could squeeze me in next week, but I will try with another mechanic. Do you think its worth trying another retest only with dipetane while i wait for the mechanic appointment or it would be wasted money?

User1998

Like I said, waste of money.

And €600 is too much for a catalytic converter

JSPD

A couple of years ago, my car failed on the emissions. My house at the time was only a short journey from the nct centre. I booked it in for the re-test 2 days after, but this time I made sure to bring it for a long spin beforehand. And it passed.

Atlantic Dawn

What was the difference in the results from the first fail test to the 2nd after the mechanic did the work?

hoodie6029

https://www.boards.ie/discussion/comment/121025995#Comment_121025995

I think at the cost of some dipetane and some petrol and €28 for the retest, it’s worth one more shot at the centre.

Bring the spare key and keep it running in the car park if they are running late. Might keep the car hot enough to pass.

GiuliaM

@Ace2007@Atlantic Dawn

The first fail was:

Engine temp 80 degrees

CO low idle (840rpm) 2.65% (failed above 0.30)

HC 117 ppm

Lambda 0.99 (range has to be between 0.97 and 1.03)

CO high idle (2810 rpm) 0.54% (failed above 0.20)

HC 4ppm

The second fail was:

Engine temp 83 degrees

CO low idle (840rpm) 0.07%

HC 8ppm

Lambda 1.00

CO high idle (2670rpm) 0.41%

HC 7ppm

Think I tagged the wrong person ace2007 sorry I'm new in this forum and I'm already making a mess

John.G

Daughter has a 2005 Polo (family owned from new) with 186,000kms, passes test, no problem, burning very little oil, maybe 2500/3000kms per litre. I renew the plugs and clean the throttle body before each test. You can clean the throttle body yourself even though these don't normally get too fouled.

Ideally, remove the air cleaner housing, switch on the ignition, put a brick or jam the accel pedal hard down to open the throttle plate fully. get a bit of rag and wet it well with WD40 or even white spirit and clean inside the throttle body with the rag wrapped around a screwdriver but don't force it too much when cleaning. When finished, remove the brick, the engine may idle a bit on the high side but will quickly self adapt and should settle down to its normal idling speed after a short drive/idle.

quartz1

i have a 2004 Polo. It failed on emissions last year and I put a new cat in for about 500 . Passed on retest and then passed this year .500 might sound a lot to spend but the way car prices are what would it cost to change the car . It serves me well and never left me down.

Field east

It is my understanding that if the car has been driven - from test to test - at low speed and at short journeys there would be a build up of carbon that may be hard to shift. So it may need a few long runs -5 mls at a time- at high revs - with Dithane for petrol engines added - to shift the carbon deposits. Check what I am saying out before considering doing the above