1.4 petrol MOT failure

ndavid

A2OC Donor
My beloved car (1.4 BBY, 2003) has failed the last emission test.

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The local service couldn't find the root cause yet. First they wanted to change the lambda sensor, but the old one was still perfect (not a surprise, it was changed 2 years ago). Then they thought the guilty one is the injector in the 4th cylinder, but no, it does not. The catalytic converter has been replaced last December. Since this check I put Cataclean to the tank and went to a 1000 km long trip, where I had 5.8 l/100km (48.7 mpg) fuel consumption.

Today I put E10 to the tank and had a second check. HC went down to 29 but the CO was still high. With a small luck and kindness the guy there was able to measure 0.2 for a moment so the car has passed the MOT, but it was really on the edge. Do you have any idea what to check still? It would be good to avoid such a situation next year...
 
I renewed my AUA's entire exhaust aft of the first cat just over a year ago. That change took my car from scraping through the emissions test on the 2nd attempt to comfortably passing first time. My CO% is now 0.10% across two MoTs, and my HC 33 and 40 ppm. It may not help you, but don't underestimate the problems that come from choked silencers (along of course with the rear cat)
 
Any fault codes?
Recent plugs? Cheap and easy
Air filter last changed?
Poor ignition or hesitant spark
MAF clean or replace if you have known good one to swap with
Temp sensor
Any of these could lead to overfuelling
 
No fault codes
Spark plugs replaced 4 years and 44.000 km ago with OEM ones (worth to change them now?)
Air filter, fuel filter replaced every year
MAF cleaned recently, I might need to check it anyway as well as the temp sensor
First part of the exhaust system including the catalytic converter has been replaced last year with an aftermarket brand, but not the rear silencer. I suspect that the one I got is not doing its job properly.(I do not know the brand name, in the bill it is listed as OE part)
 
In 2010. the CO was 0.189% and CH was 74.0 ppm. Unfortunately I have no data from the previous measurements but it seems that my car was always close to the limits. Does it mean that nothing is wrong with it, it's just like that?

Please do not laugh at me ... but I saw a Wheeler Dealers episode when the guys solved the emission problem, which was even worse than mine, by replacing the catalytic converter with a more effective one. Is there such an option for the A2?
 
In 2010. the CO was 0.189% and CH was 74.0 ppm. Unfortunately I have no data from the previous measurements but it seems that my car was always close to the limits. Does it mean that nothing is wrong with it, it's just like that?

Please do not laugh at me ... but I saw a Wheeler Dealers episode when the guys solved the emission problem, which was even worse than mine, by replacing the catalytic converter with a more effective one. Is there such an option for the A2?

Our limits here in the UK are different and are specific to the A2. At normal idle, max CO is 0.5%, at fast idle max CO is 0.3% max HC is 200ppm https://assets.publishing.service.g...-standards-for-road-vehicles-19th-edition.pdf

There is a natural variation in the levels at emission test readings from year to year, but a general tendency for emissions figures to get nearer the limits over the years as a result of natural wear and tear. Testers (as you found) are happy to look for the best result they can find to get you through and it may be that you could scrape through several more tests before you finally fail. But in truth your levels are higher than is desirable, and it would be better to find a solution.

You are quite right, cats do vary in performance. BM (the principle manufacturer of aftermarket cats here in the UK, routinely offer two grades of cat, standard and high performance. The standard cats have 200 cells, the high performance 400. https://www.bmcatalysts.co.uk/ BM sell under their own name (easily found on eBay here) and also supply many other exhaust manufacturers.

With my AUA, I only replaced the back cat, and went with the standard 200 cell option which has worked well in a stainless straight-through exhaust design. So yes, you can get better emissions performance with a more powerful cat, but my instinct is that your problem might lie elsewhere.
 
steve_c: Thanks for the info. All numbers I have quoted were measured at 3000 rpm. I have my next appointment booked already at the service (licensed VW and Seat service fixing Audis as well), because I want to fix the issue whatever it is. I will check the high performance cat option as well.
 
Fast idle in the UK test is between 2500 and 3000 rpm for the AUA and BBY engines.

You might want to contact BM and seek their advice directly.

Are you happy that your front cat is in good working order? They rarely fail, but you may be the unlucky exception to the rule.
 
Are you happy that your front cat is in good working order?

No. I asked the service to check it next time. I do not trust the place anymore, where it was fitted. (I had to go back after 1 week because the new pipe started to leak where it is connected to the rear part)
 
I realise after checking the BM site carefully that the 200 cell and 400 cell options I referenced earlier were the choices I was offered for my custom silencer (with a BM core). BM do offer a limited range of Blue Angel cats which offer higher performance, but these only cover the earlier AUA engines at the moment (thanks to @ndavid for flagging that up to me).
 
We maintain a number of Lpg vehicles on high annual mileage which are very fussy for good ignition
Prefer to use NGK bkur6et
Multi point plugs change every 20k miles
There is a noticeable improvement following change
Cheapest option if you do your own maintenance at only couple of quid each
 
I have OEM plugs, which are actually NGKs...
I am about to change the cats as I suspect my aftermarket one is not effective enough. I hope the parts will arrive next week and I can let them fitted soon.
 
Pre-catalyst, catalytic converter and silencers are all changed. The emission haven't been measured still, maybe at the MOT next year. I have spent 1.250€ so it should work perfectly. :) The parts used:
- HJS 96 11 4081 (Blue Angel)
- HJS 96 11 4204 (Blue Angel)
- IMASAF 13.01.46
- IMASAF 13.01.47

IMASAF as a brand was quite unknown to me, let's see how it lasts. These silencers were cheap at least compared to the HJSs...
 
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