MOT woes

[stevec14 10]

HI All

Been trying to get my G60 to pass the MOT for the past 3 weeks. Due to work and family commitments and weather! Had to have work done at the garage. Only failed on bottom ball joint n/s and emissions. Took car for a tune and they diagnosed the lambda sensor at fault. Had this done and it still failed on emissions! After many visits to the mot garage and tuners to get the emissions down/checked turns out my Cat has seen better days only just failing 0.5 should be >0.3 according to the test details.

When the mot test station put my reg number into the emissions test computer, it came up with all the correct chasis number and vehicle details and a registered date of 08/12/92 putting my car into needing a cat to pass the mot(cars registered after 01/08/92 need this). When I checked my V5 the car was registered 28/04/92.

A lucky escape and a mot pass at last.

Steve

[Riley 0]

Good stuff. I'm pretty sure that even if the car is supposed to have a CAT, you can actually take the test and pass without a CAT? In other words, I don't think the CAT has to be fitted, but it must pass the CAT specific test?

 

Please someone do correct me if I'm wrong!

 

Neil.

[robrado974 1]

Not sure on the rules myself , my vr failed on emmissions . Cough cough went through second time round . Mr friendly mot man !!

[stevec14 10]

Hi

Thanks for replies.

Yep mightily relieved that corrado passed MOT(knew it is a good car). Missus has been nagging me non stop since I bought it, and this was another excuse for me and the car to go our separate ways. Anyway the little I found about emissions on MOT states that any car registered after 1st August 1992 does need a CAT or confirm to the CAT test emissions to pass an MOT. That is pass a co2 test of less then 0.3 percent.

For vehicles registered between 1st August 1986 and 31st July 1992, the CO level must not exceed 3.5% by volume.

Petrol Vehicles registered after 1st August 1992 must conform to the manufacturers specification (the MOT testing garage usually checks these values on a database(sometimes wrong always double check vehicle registered date)).

The carbon monoxide level is tested at two speeds; “idle” and “fast idle”. Although the specification varies between car models, the guidelines are generally 0.5% at idle and 0.3% at fast idle.

And Hydrocarbon Emissions(petrol engines)

For vehicles registered between 1st August 1975 and 31st July 1992, the HC emissions must not exceed 1200 ppm (parts per million).

Vehicles registered after 1st August 1992 must conform to the manufacturer’s specification. The hydrocarbon level is again tested at “fast idle” speed. Although the specification varies between car models, the guidelines are generally no more than 200 ppm at fast.

Car might be up for sale soon due to a proposed long commute to work. Will find out in next month or so.

Steve

[vw rule 19]

Hello mate,

 

good to hear your car passed it's MOT and you got it sorted.

 

 

Si

[vw rule 19]

Hello there,

 

yeah the catalytic converter has to be fitted to the exhaust system on a vehicle,

other wise the exhaust emissions won't be reduced low enough,

as on most modern vehicles the ignition / fuel systems and emissions,

are governed by the cars computer system i.e ECU = (Electronic Computer Unit or Electronic Control Unit)

so in other words the fuel / emissions can be adjusted or changed,

but only if the ECU memory is reprogrammed to do so.

 

Regarding the catalytic converter it operates once the engine has been running for 10 mins or longer,

as it has to be really hot to be able to burn away harmful fumes and convert them into less harmful.

(Converts carbon monoxide into carbon dioxide = carbon dioxide is what we breath out.

Carbon monoxide is highly toxic.

 

The catalytic converter is usually fitted very close to the exhaust manifold as there is extreme heat from there,

as it's bolted directly to the engine, you can see temps of up to 350 degrees C or more from the exhaust manifold.

On vehicles like the Ford Focus and some of the Fiesta's the catalytic converter is bolted directly to the exhaust manifold,

so acts as a exhaust down pipe and emissions exhaust filter.

But on the Corrado the catalytic converter is under the car bolted to the exhaust down pipe,

in this position it's still able to obtain extreme heat from the exhaust manifold as it's still very close to it.

Inside the catalytic converter it has a honey cone like mess filter,

this slows down the waste gas flow so the heat from the catalytic converter is able to convert to less harm full gasses,

looks like as well the honey cone mesh filter inside is coated with a special metal that causes the honey cone,

to have a rough surface area this is what helps to slow down the exhaust gasses passing through the catalytic converter,

plus the extreme heat that is generated from the exhaust manifold which is transferred through the exhaust steel,

to the catalytic converter this all combines together to create a reaction which burns off or changes carbon monoxide,

into carbon dioxide.

The catalytic converter has a Lambda sensor normally fitted in it just before the honey cone mesh filter,

or it's fitted in the exhaust down pipe or in the exhaust manifold,

where ever it's fitted again it's always very close to the exhaust manifold as it only really works at high temps,

this Lambda sensor measures the exhaust gasses just before they enter into the catalytic converter,

if the sensor picks up any rich readings like unburnt fuel deposits,

it communicates with the ECU which has the cars running data in its memory chip,

so if the sensors readings don't match what's on this memory chip,

the ECU will adjust accordingly until the set readings are matched again.

The Lambda sensor helps to reduce the emissions down quite low but not low enough,

so thats where the catalytic converter comes in.

 

THE ECU DOESN'T KNOW WHEN THE CATALYTIC CONVERTER HAS BEEN REMOVED,

THE ENGINE WILL STILL RUN NORMALLY AS LONG AS THE LAMBDA SENSOR IS STILL FITTED,

THE ECU ONLY CONTROLS THE SENSORS = IT HAS NOTHING TO DO WITH THE CATALYTIC CONVERTER,

SO REMOVING IT WILL 100% CAUSE YOUR EMISSIONS TO BE OVER THEIR LEGAL LIMIT,

AS IT'S PURELY THE CATALYTIC CONVERTER THAT CONVERTS THESE HARMFUL FUMES IN QUESTION.

 

In the MOT test the emissions are checked via a cryptic analysis computer,

normally a tacho sensor is connected to one of the HT leads on the older cars, like on our Corrado's,

and a oil temp probe sensor is put down into the dip stick tube to measure the oil temp,

and finally a emission probe is put up the exhaust tail pipe.

 

1) Tacho sensor = is to read the cars RPM

2) Oil temp probe sensor = is to measure the engines temp

3) Exhaust probe = picks up the exhaust gasses for analysis.

 

Once the cars engine is up to the correct operating temperature,

the MOT tester will rev the engine to about 2500 RPM for roughly 30 seconds to 1 min,

and it's tested again at normal idle speed.

This is the testing procedure for checking the catalytic converters performance,

so if a catalytic converter has been removed off the car the emissions will fail with out question.

Some people do remove the cat and fit a decat pipe but once the MOT is coming up,

they change it back so the car will pass it's MOT emissions test.

 

Below was taken off the MOT site.

 

1) Where engine speed can only be measured by the removal of a cosmetic engine cover,

the speed measurement must still be carried out if the cover can be easily un-clipped.

If engine speed cannot be measured then the vehicle tachometer should be used if fitted.

Otherwise engine speed measurement may be by-passed and a subjective estimate made.

 

2) Engine oil temperature must be measured whenever possible,

using the approved temperature probe.

Where, in exceptional circumstances, the engine oil temperature cannot be measured

(e.g. in the case of a dry sump engine), check that either:

 

A) the temperature gauge indicated that the engine was at its normal operating temperature

B) the cooling fan had cut in, or

C) the coolant pipes were hot.

 

Below as stated in STEVEC14 last post.

The catalyst (Cat) test is part of the MOT test for most spark ignition petrol engined passenger cars,

with four or more wheels first used on and after 1 August 1992.

Carbon monoxide (CO), Hydrocarbons (HC), and lambda sensor (~) are all checked,

at fast idle e.g (between 2500 RPM and 3000 RPM),

and carbon monoxide (CO) is checked again at idle speed.

 

 

Hope this helps

 

Si

Edited April 13, 2014 by vw rule

[Stonejag 10]

My '95 VR6 passes its emissions test at the MOT every year. In my ownership it has never had a cat fitted. If the engine's healthy you can still be below the emissions limit without a cat fitted. Helps if you take it for a good run first ;)

 

Stone

[Liam20vT 10]

My '94 20vT hasnt got a cat fitted and passed the emissions test no problem. Glad you got it sorted though!

 

Liam

[n3p 3]

Could someone confirm if a CAT actually needs to be present in order for it to pass? (ie a visual inspection)

 

I've been told of a loophole re. a VR6 Turbo, as there are no specified emission values for a turbo VR (hopefully this is true), and as my MOT is looming I'm wondering if I could save on not buying a sports cat...

[g0ldf1ng3r 15]

Could someone confirm if a CAT actually needs to be present in order for it to pass? (ie a visual inspection)

 

I've been told of a loophole re. a VR6 Turbo, as there are no specified emission values for a turbo VR (hopefully this is true), and as my MOT is looming I'm wondering if I could save on not buying a sports cat...

 

Hi Nick - i cant comment on your question....but....i did pose the similar question & was told there are 'friendly' places ;)

PM me if that is too cryptic lol

Edited April 14, 2014 by g0ldf1ng3r

[Graphite 0]

It is completely possible for engines to pass the emissions tests without a catalytic converter, My mk4 4mo has no cats in and it passes every time. An engine that has had regular oil and filter changes as well as fuel filter changes can pass no problem given that all the control equipment (ECU, the map on that ecu, lambda probe) are all working within parameters.

 

As far as I am aware if the emissions for a cat registered car are below the requirements to pass the emissions test regardless of whether there is a cat installed or not, it should pass. There is no visual inspection element as far as I know of, if anything is noted, it would probably be an advisory.

 

Could someone confirm if a CAT actually needs to be present in order for it to pass? (ie a visual inspection)

 

I've been told of a loophole re. a VR6 Turbo, as there are no specified emission values for a turbo VR (hopefully this is true), and as my MOT is looming I'm wondering if I could save on not buying a sports cat...

 

The original engine fitted to the vehicle will be stated when the details are pulled up through the registration number (if the modification hasn't been officially changed with the DVLA), however all cars registered with cat requirements are checked against with the same requirements, the only time the requirements have changed is over the years where the legislation has become more stringent (Euro 2,3,4,5 and now going into Euro 6) So for example vehicle registered in 1994 will be able to pass with higher emissions values than a vehicle registered in 2004.

 

There is no loophole because the engine has had a turbocharger retrofitted, if the V5 document hasn't been changed to support the modifications then it would be tested to the specification of the original engine. Even so, if the engine has been changed on the V5 the engine would have to conform to the pass values of the year of the chassis anyway...

Most testers will just go by what their screens pull up. The whole process is automated and it automatically gives them the pass values for the given car on screen against what the car is actually putting out when tested.

 

If in doubt the best thing to do is be honest with your local test center, they may help you in certain ways (legal or not). The other option is to find a workshop that own a gas analyser, find out what the pass values for your car are, and test the car in exactly the same way as the MOT center. The only problem with doing this is that everyone's equipment varies and give different results, also an independent garage may not get their equipment calibrated where as the MOT centers have to ensure their equipment is.

Edited April 24, 2014 by Graphite

[n3p 3]

Thanks for the detailed reply, I did think it sounded too good to be true. I didn't even think you had to notify the DVLA of a turbo. May well have to now in order to keep everything above board.

 

Re. the visual inspection of a cat, I've read varying opinions and apparently the law changed in 2012 stating that a cat needs to be present. How true that is I don't know, but I have my MOT booked later today so I'll find out :)

[g0ldf1ng3r 15]

Thanks for the detailed reply, I did think it sounded too good to be true. I didn't even think you had to notify the DVLA of a turbo. May well have to now in order to keep everything above board.

 

Re. the visual inspection of a cat, I've read varying opinions and apparently the law changed in 2012 stating that a cat needs to be present. How true that is I don't know, but I have my MOT booked later today so I'll find out :)

 

good luck nick - let us know how you get on!

[Kempy 0]

My valver has a straight through pipe, no cat. Never had problems with emissions. I do have friendly testers though..

[Portent 0]

Thanks for the detailed reply, I did think it sounded too good to be true. I didn't even think you had to notify the DVLA of a turbo. May well have to now in order to keep everything above board.

 

Re. the visual inspection of a cat, I've read varying opinions and apparently the law changed in 2012 stating that a cat needs to be present. How true that is I don't know, but I have my MOT booked later today so I'll find out :)

 

Yes I believe the law changed in 2012 and a cat must be present if the car had one originally. Some people leave the cat in place but gut the internals.

[Graphite 0]

Interesting, I wasn't aware of this. Well looks like gutting will become more common if this is true.

Edited April 27, 2014 by Graphite

[Dox 23]

Post 1992 K plate the car has to be fitted with a cat when tested if the car left the factory with one.

 

If you have a post 1992 car and can prove it has an engine fitted that's pre 1991 J plate and older it will be tested as such and wont need a cat.