Failed MOT today

RZX

Member
Hello all you wonderful people. My much loved FSI failed it's MOT today on emissions and only that, no advisories for anything else.
I have messaged WOM but no response as yet and they are not answering the telephone either.
Anyway in the meantime advice from you knowledgeable people is always welcome.
The garage that did the MOT said they could replace the cat price approx £450. I am not about the cost to repair (within reason)it's about having faith in the repairer hence contacting WOM. Does anyone know of a garage in Lancaster area that might be able to assist if WOM can't.

So I am asking will emission failure be only done to the cat or are the other things it could be as well, also any recommended garages in Lancashire area.
I do want to keep the car as it was my first A2 bought on a whim 3.5 years ago and like so many people on here I am now addicted to these lovely little cars.
I would add I always use at least 98 fuel.
Thanks
 

Jellybean

Admin Team
Tip a can of Cat Clean in the tank, and take for a good clearout?

Sent from my SM-N960F using Tapatalk
 
  • Like
Reactions: Nye

timmus

A2OC Donor
Does anyone know of a garage in Lancaster area that might be able to assist if WOM can't.
Despite being in the Lancaster area, I don't have great knowledge of the local garages. Like you, where dirty stuff is concerned, I'm a WOM loyalist.

Are we sure that a replacement catalytic converter will solve the problem? Is this a definitive diagnosis by the garage who did the MOT, or their best guess?

Cheers,

Tom
 

Rusty911

A2OC Donor
Or even ... most profitable guess.

Everyone's flying blind until some basic checks have been done: pulling the codes, inspecting for air and exhaust leaks, checking air filter and so on.

Yes, if everything else checks out and watching live data shows no / little difference between exhaust pre and post cat, then yes, finally you can say cat. Even then, you'd still try running a cat cleaner through it: Cataclean seems to have a genuinely fantastic reputation. It won't rescue a holed converter, but it might make the difference between a marginal fail and a pass.

Was it a catastrophic fail or a near miss?
 

RZX

Member
Tip a can of Cat Clean in the tank, and take for a good clearout?

Sent from my SM-N960F using Tapatalk
I did that yesterday as I feared emissions maybe a problem due to 4 months of only short journeys, took it for a 40 mile blast up the M6.
Thanks
 

RZX

Member
Despite being in the Lancaster area, I don't have great knowledge of the local garages. Like you, where dirty stuff is concerned, I'm a WOM loyalist.

Are we sure that a replacement catalytic converter will solve the problem? Is this a definitive diagnosis by the garage who did the MOT, or their best guess?

Cheers,

Tom
Their best guess I think hence I don't want to give them the job. Maybe best to wait for Rob or Marcus to contact me.
Thanks for your help
 

RZX

Member
Or even ... most profitable guess.

Everyone's flying blind until some basic checks have been done: pulling the codes, inspecting for air and exhaust leaks, checking air filter and so on.

Yes, if everything else checks out and watching live data shows no / little difference between exhaust pre and post cat, then yes, finally you can say cat. Even then, you'd still try running a cat cleaner through it: Cataclean seems to have a genuinely fantastic reputation. It won't rescue a holed converter, but it might make the difference between a marginal fail and a pass.

Was it a catastrophic fail or a near miss?
 

Attachments

PlasticMac

Member
Get a VCDS scan done. It will, probably, answer your question:
"So I am asking will emission failure be only done to the cat or are the other things it could be as well"
Mac.
 

Rusty911

A2OC Donor
Ouch! That really wasn't a near miss.

Does the car use lots of oil? Has it had long standing misfires / rough running / dropping cylinders / mis-fueled with diesel? Mileage? Cats are actually pretty reliable if treated well and often they fail as a result of being pushed too hard in some regard.

This is important because (like fitting a new turbo with the old, dirty oil lines) you want to make sure that if you do indeed end up with a new cat, it doesn't quickly also get damaged. I.e. it might get you the ticket only for you to be back here again in a test or two.
 

steve_c

A2OC Donor
Ouch! That really wasn't a near miss.

Does the car use lots of oil? Has it had long standing misfires / rough running / dropping cylinders / mis-fueled with diesel? Mileage? Cats are actually pretty reliable if treated well and often they fail as a result of being pushed too hard in some regard.

This is important because (like fitting a new turbo with the old, dirty oil lines) you want to make sure that if you do indeed end up with a new cat, it doesn't quickly also get damaged. I.e. it might get you the ticket only for you to be back here again in a test or two.
The FSI is a strange beast, that exhausts unburnt petrol (which burns in the cat to reduce NOx). Original cats were made of an exotic and unique combination of elements and have not been available for many years.

The only long-term solution is the Pro Boost remap which means one can then fit a conventional cat without any issues:
 

A2Steve

A2OC Donor
+1 for cataclean, it really does do what it says on the tin. Got me through 2 MOT failures on emissions so far.
 

Rusty911

A2OC Donor
The FSI is a strange beast, that exhausts unburnt petrol (which burns in the cat to reduce NOx). Original cats were made of an exotic and unique combination of elements and have not been available for many years.

The only long-term solution is the Pro Boost remap which means one can then fit a conventional cat without any issues:
Crumbs! Every day's a school day!
 

RZX

Member
Ouch! That really wasn't a near miss.

Does the car use lots of oil? Has it had long standing misfires / rough running / dropping cylinders / mis-fueled with diesel? Mileage? Cats are actually pretty reliable if treated well and often they fail as a result of being pushed too hard in some regard.

This is important because (like fitting a new turbo with the old, dirty oil lines) you want to make sure that if you do indeed end up with a new cat, it doesn't quickly also get damaged. I.e. it might get you the ticket only for you to be back here again in a test or two.
Hi, no long standing issues, a couple of years ago had a misfire, sorted with earth behind headlight and replace coils, has behaved fine since then. Certainly no misfuel and mileage is 80000.
Thanks for your input
 

nolan

Member
The lambda value is out so I would start by looking at the oxygen sensor, don't know much about VCDS but presumably it will be able to show the lambda value and whether the sensor is working correctly. I don't think a new cat would fix this.

A low value indicates it's running rich, does the car use more fuel than you think it should?
 

RZX

Member
The lambda value is out so I would start by looking at the oxygen sensor, don't know much about VCDS but presumably it will be able to show the lambda value and whether the sensor is working correctly. I don't think a new cat would fix this.

A low value indicates it's running rich, does the car use more fuel than you think it should?
Last fill up an average of 39mpg which is lower than in the past but I thought that was because only local work for the last 300 miles.
Thanks for your thoughts
 

audifan

A2OC Donor
Assuming all the normal service parts ( filters, plugs etc ) are known good and you are running on recommended fuel. I would put Cataclean into the tank when low on fuel. Take the car for "an Italian tune-up" to get things nice and warmed through. Now take it for an emission test. You did not say how badly or border line the failure was. Looks like another candidate for @A2Steve modded ECU.
 

timmus

A2OC Donor
Hi folks,

@RZX is visiting me tomorrow morning in order for me to have an investigate with VCDS. Scanning the ECU for fault codes is obviously Step 1, but what do FSI aficionados recommend that I do thereafter?
I'd consider the A2's petrol engines to be the great hole in my knowledge, simply because I don't own one. Using measuring blocks, for instance, how can I establish whether the catalytic converter is doing its job? Could someone please give me a bit of information about the pre- and post-cat sensors and how to locate/interpret their readings.

Thank you!

@steve_c , @Andrew , @ajsellors ... you three immediately pop into my head.

Cheers,

Tom
 

Andrew

A2OC Donor
Sorry no help, little knowledge of exhaust system, never had reason, @steaman I think.

I can offer to mirror any measuring blocks for comparision if that helps, but like RZX I imagine my system is not healthy with predominantly short trips.

Andy
 

ajsellors

A2OC Donor
The lambda values in the test results are very low, and outside the permitted range which is why it failed on lambda.
The lower the value the more rich the fuel mixture is. Too rich and there will be a high CO content and so that will fail too.
Only the pre-cat lambda sensor is used for fuel trim so the cat won't be affecting the fueling. Although the cat can't be ruled out I wouldn't say it is the primary problem. Running an engine rich for a long time can damage the cat as it overheats due to the excess fuel.
I would say understanding the low lambda value should be the first port of call for diagnostics.
 
Top