NCT Failed

Paulbut2000

Hey people. My car failed the NCT on Friday , it failed on one thing and that was the exhaust emissions, the high idle (2,930 rmp) /CO volume was 0.32% with the limit being 0.20%. , the lambada was 1.00 which passed , had to be between 0.97-1.03.

I drive an Audi A4 petrol 1.6 2005.

Is this CO failed reading close to passing or a very bad reading. Everything else passed on the test so just wondering if there's a quick fix to get it over the line? Any suggestions?

shooter88

It could just be choked up,did you put in any fuel treatment before test and drive it hard(use a lower gear than usual

George Dalton

Obviously an internet diagnosis is difficult but the problem is most likely to be the catalytic converter. The lambda of bang on 1.00 means the car isn't running rich or lean which is good. The fact that it passed the low idle CO but failed the high idle means that the cat is past its best and while it can do a sufficient job to get the CO down at low idle, it can't keep up with the increased flow of gases at high idle.

As posted above if you use a good fuel system treatment and give the car an "Italian tune-up" it might just scrape through the retest. If not then it is time for a new cat.

Stella Virgo

before buying/replacing anything,remove the lambada/o2 sensor from the cat and clean it using mild sandpaper and wd40, clean out any slots/holes as the are probaly blocked with carbon,this sensor is cruicall for emissions and smooth running of engine.you will need a special slotted socket to remove it.