Failed MOT emissions

[Nick9one1]

Failed my MOT yesterday on emissions (and cracked wheel!).

The natural idle was fine, it failed on fast idle.


I have primary cats removed. Although reading on here and other forums this shouldn't cause a fail. Loads of people pass without them.
Its been recently serviced.

the car had an unknown ECU tune which I've just removed with MHD.
No codes stored in INPA

Any suggestions?


Couple of pics from INPA (not sure if these suggest anything?)

 

[Anonymous]

Failed my MOT yesterday on emissions (and cracked wheel!).

The natural idle was fine, it failed on fast idle.
IMG_20180513_171313.jpg

I have primary cats removed. Although reading on here and other forums this shouldn't cause a fail. Loads of people pass without them.
Its been recently serviced.

the car had an unknown ECU tune which I've just removed with MHD.
No codes stored in INPA

Any suggestions?


Couple of pics from INPA (not sure if these suggest anything?)
IMG_20180513_152515.jpg
IMG_20180513_152507.jpg

PA3 3FG.PA3 3FG.


HI your MOT failed on both tests, worse on normal idle...

It would suggest that either fuelling is wrong which seems less likely baaed on the othe numbers ...it would appear that your cats that remain are not working well enough..............

OBviously a hand flashed re-map is drought with perils...are you 100% certain that the s/w is 100% original now?

If so then. It’s your Cats or. Rogue injector..but you would notice that probably on tick over?

 

[Nick9one1]

What I mean is it passed the first 'natural idle' test.

It failed the fast idle - they perform a second longer fast idle test if it fails the first fast idle. It's a longer run the second time to allow the cats to heat up.

The second fast idle did have a better result. 0.61 down from 1.00 but still way above the pass mark of 0.20.

The car has has 6 new injectors within the last year. I calibrated them myself through INPA.

it's definitely running a standard tune now. If you're familiar with MHD you'll know you can choose 'Stock' from the map options. It takes about 40 minutes to write it to the DME.

I think my best bet is to service it (due anyway), get it red hot and take it again. Along with the stock map it might slip though.

I've also just bought some cat cleaner. I'm normally very skeptical of additives, but it has fantastic reviews on amazon.

Cataclean 500ml Engine and Catalytic Converter Cleaning Treatment https://www.amazon.co.uk/dp/B002BVXM92/ref=cm_sw_r_cp_apa_i_uJt-AbENCWPWD

 

[Anonymous]

What I mean is it passed the first 'natural idle' test.

It failed the fast idle - they perform a second longer fast idle test if it fails the first fast idle. It's a longer run the second time to allow the cats to heat up.

The second fast idle did have a better result. 0.61 down from 1.00 but still way above the pass mark of 0.20.

The car has has 6 new injectors within the last year. I calibrated them myself through INPA.

it's definitely running a standard tune now. If you're familiar with MHD you'll know you can choose 'Stock' from the map options. It takes about 40 minutes to write it to the DME.

I think my best bet is to service it (due anyway), get it red hot and take it again. Along with the stock map it might slip though.

I've also just bought some cat cleaner. I'm normally very skeptical of additives, but it has fantastic reviews on amazon.

Cataclean 500ml Engine and Catalytic Converter Cleaning Treatment https://www.amazon.co.uk/dp/B002BVXM92/ref=cm_sw_r_cp_apa_i_uJt-AbENCWPWD

Cats do fail, and can get damaged through mis fueling so it could be that some combo of use/abuse and the missing cats all add up to taking you over the edge...magic lotions may work...interested to see if they help...lot cheaper than new cats...

I’m surprised still that with the new MOT check that you can pass with one set of cats deleted..

 

[Nick9one1]

When you say the new MOT check you mean the visual check? - the fronts are completely hidden by the undertray so no way you can tell.

Cats do fail, and can get damaged through mis fueling so it could be that some combo of use/abuse and the missing cats all add up to taking you over the edge...magic lotions may work...interested to see if they help...lot cheaper than new cats...

I’m surprised still that with the new MOT check that you can pass with one set of cats deleted..

Yes I realise they can fail, although I've never experienced it myself - I had a 20+ year old Porsche 944 S2 that still had original cats.

I'm interested to see if the cat cleaner works too. Although because its been serviced and running a different map, a pass isn't going to conclusively prove the 'potion' works.

 

[Anonymous]

When you say the new MOT check you mean the visual check? - the fronts are completely hidden by the undertray so no way you can tell.

Cats do fail, and can get damaged through mis fueling so it could be that some combo of use/abuse and the missing cats all add up to taking you over the edge...magic lotions may work...interested to see if they help...lot cheaper than new cats...

I’m surprised still that with the new MOT check that you can pass with one set of cats deleted..

Yes I realise they can fail, although I've never experienced it myself - I had a 20+ year old Porsche 944 S2 that still had original cats.

I'm interested to see if the cat cleaner works too. Although because its been serviced and running a different map, a pass isn't going to conclusively prove the 'potion' works.

With the oem map and the drain cleaner it should do it....not sure what the first stage cats do and why their removal has little impact?

 

[Nick9one1]

I think first stage cats are normally for reducing emissions on a cold start.
Once the engine is up to temperature they dont do much and the secondary cats are more efficient.
The combination reduces emissions overall, giving the car a lower lower tax band.

there are loads of people with 335i's that have no primary cats and get through an MOT fine.

 

[mcbutler]

We will probably see more of this as cars with tampered cats are weedled out. They can fail you now just for evidence of Cat tampering (and notify the RSPCA as well )...

 

[Nick9one1]

We will probably see more of this as cars with tampered cats are weedled out. They can fail you now just for evidence of Cat tampering (and notify the RSPCA as well )...

That's why it's popular to swap out the front cats - you cant see them when the engine undertray is installed.

 

[mcbutler]

We will probably see more of this as cars with tampered cats are weedled out. They can fail you now just for evidence of Cat tampering (and notify the RSPCA as well )...

That's why it's popular to swap out the front cats - you cant see them when the engine undertray is installed.

Cunning.......

 

[andyfanshawe]

I would want to see graphed data from the post CAT oxygen sensors to make any definitive judgement. Snapshots are no good.
CATACLEAN is a superb place to start for the DIY'er. I have used it many times with incredible results.

Being in the trade I have to make quick 100% decisions as much as possible.
I would scope the pre and post cats and do an oxygen storage test (snap throttle and see how much time it takes for the post cat to react to the extra oxygen). Sounds a lot more complicated than it actually is!!

Make sure you have no exhaust leaks whatsoever. Even the smallest crack can create havoc.

Andy.

 

[Ewazix]

+1 on Andy's observations. Catclean and a really close inspection for manifold and joint leaks

My old scooby turbo failed massively last year (idle was OK but something like 10x at fast idle!) Catclean brought it down significantly, then finding a tiny split under an exhaust bracket sorted it fully and it's passed again no problem since.

 

[Nick9one1]

Thanks Andy that's some good advice.

Unfortunately the o2 sensors are either side of the front cats (which have been removed). So the second sensor won't give any useful info on the state of the remaining catalytic converters.

I presume any exhaust leaks before the o2 are the important ones as they would skew its reading and fueling?

Cat clean should arrive tomorrow so should have it back in for a retest by the end of the week.

 

[Nick9one1]

Being tested right now.. Fingers crossed

 

[Nick9one1]

Fail again..

He didn't give me another fail certificate as I'd have to go though the whole test again. Instead I've got 1 week left to have another retest.

It was reading 1.045 - higher than last time!

He did say there was a slight leak just before the backbox which could be causing it.

I should have asked him to test both sides, but I forgot!

 

[Ewazix]

Fail again..

He didn't give me another fail certificate as I'd have to go though the whole test again. Instead I've got 1 week left to have another retest.

It was reading 1.045 - higher than last time!

He did say there was a slight leak just before the backbox which could be causing it.

I should have asked him to test both sides, but I forgot!

As suggested, a tiny leak can throw it right off and mess the cat due to the misfuelling, sorting the leak and a dose of Catclean will help.

 

[Nick9one1]

With the leak being after the cats/o2 I didn't think it would matter, but I'll fix it and try again.
On the second dose of catclean now.

 

[Nick9one1]

Just had the emissions checked at a different garage and it passed with flying colours now the leak is fixed.

Booked in for the retest at 2pm.

 

[Ewazix]

Just had the emissions checked at a different garage and it passed with flying colours now the leak is fixed.

Booked in for the retest at 2pm.

It's amazing how a tiny leak can really screw things, your MPG should improve no end as well

 

[Nick9one1]

You're right! With the hole being so far back I didn't expect it to skew the reading so much.

It was massively under the maximum limit of 0.2 with a score of 0.06.

So you definitely can pass emissions with primary cats removed!