NCT emmissions pass :)

andrew_ireland

Just wanted to share a quick fix that worked for the dreaded NCT Emmissions test.
Last Sunday, 8th July, my 1999 E46 BMW failed on emmissions- the CO levels were at 0.56% when they should have been below 0.30% at high idle 2560rpm.
This morning I had it retested and the emmissions were 0.01% CO at high idle so it passed

From chemistry class in school (a long time ago ) I remembered that CO is released at incomplete combustion i.e not enough oxygen. Had a look at the air filter and it was bad.......very bad.

Changed the air filter and drove about 1000 miles over the week with about half a litre of Dipetane in the tank and that did the job.

By the way, does anybody else have a problem with an obnoxious smell of fumes in the car after the NCT? Happened on both the first and second attempts at the test but doesn't happen when I'm driving.

Matt Simis

andrew_ireland wrote: »

By the way, does anybody else have a problem with an obnoxious smell of fumes in the car after the NCT? Happened on both the first and second attempts at the test but doesn't happen when I'm driving.

At a guess Id say its because they rev it stationary and your air vent flap in the boot is stuck open or letting in air from outside. Wont matter really when driving, just when sitting in traffic.

andrew_ireland

I'll check the vent later on today, thanks for the suggestion. Although I didn't recognize the smell even as I'd sit in traffic. It smelt a bit like a diesel car (mine is a petrol engine) running on cooking oil only much stronger.

Miley2

Sorry to hijak but its a related question.

If you have an Emissions Warning light on the dash but your emissions are ok, will you pass?

Its a VW Passat 1.9 tdi

Dirkster

Wouldn't think so. Any warning light on the dash is a failure. take the bulb out..

wonski

Dirkster wrote: »

Wouldn't think so. Any warning light on the dash is a failure. take the bulb out..

Worst advice you could give. Think again.

Not every warning light is a NCT failure.


Sorry - it is a diesel, so there could be a problem..., still better to find a reason, unless it is to expensive to fix.

Leonard Hofstadter

Dirkster wrote: »

Wouldn't think so. Any warning light on the dash is a failure. take the bulb out..

That is shocking advice, and the kind of thing only a seriously dodgy back street mechanic would do.

Anyway, the NCT now check to make sure that all warning lights come on when they're supposed to, and the engine light being on in a diesel WILL fail the NCT (and rightly so, considering that diesels aren't tested for emissions in the way a petrol engine is - only for smoke).

The engine light in a petrol engined car is NOT on its own grounds for NCT failure, however if the engine light is on because of an emissions related fault then the car will fail the NCT on emissions.

Miley2

Had it in my own mechanic for a week and he couldnt solve it.
Will just have to bite the bullet and bring it to a dealer.
I have read this is often caused by a faulty break light switch but not in my case

nogoodnamesleft

Dirkster wrote: »

Wouldn't think so. Any warning light on the dash is a failure. take the bulb out..

Worst possible advice anyone could give.

I noticed that when my Passat was in for the NCT in the past 2 occasions it was connected up to a ODB2 computer during the emissions test phase.

Emissions warning light is most likely a temperature sender unit and is much easier to replace that pulling a bulb and it solves the problem rather than hiding it. A scan would confirm or discount this diagnosis.

Here is a post I wrote a while ago regards replacing it if you fancy changing it yourself:

http://www.boards.ie/vbulletin/showthread.php?t=2055757452#8