MOT went fine today apart from it failing on the emissions. :(

The garage were pretty good, they ran some Forte treatment through it in case the engine was coked up a bit, and we gave it a good 20 mile pretty hard run before testing it again, but it was still too high on CO2 on the 2500-3000rpm test. It was fine on the idle test.

The only mods I've got are a stage 1 remap, piperX panel filter (done 10k) and a 007p. No changes to the exhaust or a decat or anything like that.

Lamda was fine, HC was fine but CO2 is at 0.66% (max 0.30% for a pass).

Anyone have any ideas what would cause the CO2 to be high at those revs, but ok at idle?

Mine failed on emissions last year the VW man said that the earths should be cleaned and the lamda sensor. Re tested the car and it passed.

The map might be over fueling at revs ?

The map might be over fueling at revs ?

+1 agree

You may find that as the MOT rev test runs revs at approx 3250 rpm that can be just the wrong rev range to cause fuel / air ratio issue with certain mapping.

I had the exact same issue after first replacing O2 sensors and a new sports cat. doh.

The map was ok on idle and after that rev range. It was quite an aggresive map

I had the map taken off and replaced with a decent tuners map and sailed through MOT.

The emissions test engine speed is as per the test instructions. They'll start off with a basic emissions test where the fast idle will be 2500 to 3000 rpm, if the car fails this then it goes to a more involved vehicle specific test involving inputting the engine code. With this data, the fast idle speed could be possibly specified by the manufacturer at a different limit.

One point to note is that CO2 is carbon dioxide, though emissions of this are used to calculate vehicle excise duty bands, it is not measured on the MOT. Carbon monoxide (CO), hydrocarbons and lambda are measured.

Does removing the air filter have any effect?

I had a similar problem with high fast idle co (0.8) which was cured by a new lambda.

If ever there was a better excuse for the misses to buy a miltek system, here it is!

You're welcome to my old cat/downpipe if you need it foc.

Thanks for the advice guys. I spoke to Will at performance torque and he advises me to get the MAF checked as the first possible culprit. The fuelling map is unchanged until 40% engine load apparently.

So I now need to find somewhere relatively local to get it checked and possibly logged. Awesome are fully booked until the middle of next week, does anyone know anywhere in the Lancs area that might be able to help?

40% of 7000rpm would be 2800rpm, so that fast idle would be about when the map is changing fuelling no?

40% of 7000rpm would be 2800rpm, so that fast idle would be about when the map is changing fuelling no?

40% of engine load, old bean, not engine rpm. At fast idle the load would apparently be about 5% whereas towing a caravan uphill it would be 100% if ya get my drift.

Thanks for the advice guys. I spoke to Will at performance torque and he advises me to get the MAF checked as the first possible culprit. The fuelling map is unchanged until 40% engine load apparently.

So I now need to find somewhere relatively local to get it checked and possibly logged. Awesome are fully booked until the middle of next week, does anyone know anywhere in the Lancs area that might be able to help?

I still think that you should get the fuelling of the map checked out before you part with cash for a MAF, as a map can cause overfuelling at that RPM range as mine is proof of it.

Perhaps you could post your emissions reading. should be within 0.3 at raised rpm. Mine was 1.6

It was 0.63 at fast idle

The prob for me with getting the map checked is it's a 200 mile round trip and a day off work. Not sure what I'm gonna do at this point. Ideally, getting the mac readings logged and possibly swapped for another one to see if it makes any difference.

Emissions are such a pain in the backside aren't they! You're chasing an invisible target, and it's not even like I can check them myself to see if somethings worked or not.

It was 0.63 at fast idle

The prob for me with getting the map checked is it's a 200 mile round trip and a day off work. Not sure what I'm gonna do at this point. Ideally, getting the mac readings logged and possibly swapped for another one to see if it makes any difference.

Emissions are such a pain in the backside aren't they! You're chasing an invisible target, and it's not even like I can check them myself to see if somethings worked or not.

Tell me about it. After mine failed i changed 02 sensors and then sports cat for another one, thinking that would do it. ( out of pocket big time) and then MOT retest still failed for identical readings, I was not impressed.

JKM were good as they spent some time logging the mapping and fuel / air mix and then found a really bad fuel mix at exactly 3250 rpm that caused the massive reading i had Map taken off and back to standard which brought the fuel mix way below the pass rate. (it was a postal remap :'( )

I hope it is your MAF as at least that can be sorted reasonably easy and not massive cost.

Your readings are not too bad and may point to a MAF?. I have seen higher reading initially that has passed on a second run with a good thrash before the test.

I missed my Map so ended up with a REVO, wallet sure took a dent that week.

Luckily I sold the Blueflame sport cat and recouped some money back.

Edited 27 September, 201015 yr by Bowders1

I would imagine Will has used this map many times for the Vrs so doubt it would be that...... but I maybe wrong lol.

Mark your old map was a one off made by Diga-tec so prob not used on another car.

Edited 27 September, 201015 yr by martziniuk

I would imagine Will has used this map many times for the Vrs so doubt it would be that...... but I maybe wrong lol.

Mark your old map was a one off made by Diga-tech so prob not used on another car.

Hey buddy nice to hear from you over on the MK1 side. You probably right but it was worth mentioning, as i have heard maps being the issue on several cars in the past.

Hey buddy nice to hear from you over on the MK1 side. You probably right but it was worth mentioning, as i have heard maps being the issue on several cars in the past.

Hey Mate I see your mod sig has grown BIG time lol. Certainly is worth mentioning, it could be owt even a busted cat.

Spoke to my pal yesterday who used to work at VW/Audi and is an MOT tester.

He says if the cat is bust, usually it will fail the natural idle test (as the rpm are not enough to get the cat hot) but pass the fast idle test because the cat then gets hot enough. In my case it's the opposite way round so it would point to a sensor. The question is which one!

http://briskoda.net/forums/topic/97103-failed-emissions-test/page__p__1198057__fromsearch__1entry1198057

Lambda 1

Edited 28 September, 201015 yr by Liverpool-Lad

I was doing the MOT in june this year....everything went fine but my emmisions were high at idle because that idiot forgot to turn my AC off!

I was lucky because I saw him trying to turn my clima OFF ,but was still ON on low ventilation at 19 degrees Celsius

Edited 28 September, 201015 yr by IulianE

40% of engine load, old bean, not engine rpm. At fast idle the load would apparently be about 5% whereas towing a caravan uphill it would be 100% if ya get my drift.

I get what you're saying, but I'm a touch surprised they do that.

Still hey ho.

Well I got it sorted today at last. I took it to a Votex in Congleton, a really great bunch of VAG specialists who have a lot of enthusiasm for anything VAG. They have a lot of experience tuning fast Audis in particular and are a Revo franchise.

It wasn't a cheap day since it needed a new cat, and I was advised to replace the lamda sensor at the same time. Anyway once that was done it was tested again and is now nice and low, well under the CO limit.

I think I'll be using Votex again in future, highly recommended.