MOT Emissions Fail

[Hillsie]

My C Class has failed on emissions. My mechanic has changed a few of the sensors which helped a bit but it still hasn't passed. The next step is to replace the cat which I don't have the funds to do when it might not even fix the issue. Does anyone know a good MOT test centre in Essex?

 

[whitenemesis]

How badly has it failed?

Possibly try a good "italian tune-up" just prior to the retest?

 

[Hillsie]

Apparently its failed massively. On the verge of having to sell it for a fraction of its worth which is a real shame

 

[zipdip]

My C Class has failed on emissions. My mechanic has changed a few of the sensors which helped a bit but it still hasn't passed. The next step is to replace the cat which I don't have the funds to do when it might not even fix the issue. Does anyone know a good MOT test centre in Essex?

Well you need to give the car a serious revving say two minutes at 3000 revs just before the MOT starts,it is all about the heat of the exhaust when the car is tested,you could also in the early morning put a lot of redex into your fuel tank with only say a quarter of a tank full of diesel/petrol,then find a deserted area and drive it in low gears reviving the engine there will be clouds of black smoke after that goes fill up with fresh diesel/petrol,and test the car.

 

[clk320x]

Does anyone know a good MOT test centre in Essex

Lol A ‘good’ MOT centre

 

[Deletedmember130310]

Lol A ‘good’ MOT centre

Easy to find - it has some rocking horse poo outside.

 

[Hillsie]

Good test centres are hard to find

 

[Martin 1]

As well as the above, do an oil change, and a new air filter, I'm serious ! Have you read the codes looking for sensor failure. Don't give up !

 

[Hillsie]

Had a merc specialist look at all the codes and he has said its most likely the cat but he can't be 100% sure it will fix the issue. I'm already £800 in and I can't afford to spend anymore

 

[DSM10000]

Good test centres are hard to find

What do you mean by a "Good" test centre? One that will overlook the emissions value(s) that "massively" failed?

 

[estate-agent]

Knowing what the reading from the emission test would be helpful here. Hard to diagnose without seeing the Co reading and PPM reading. Usually a lambda sensor faulty but if no fault codes are showing then it could be as simple as poor combustion due to wrongly gapped spark plugs or filthy air filter making the fuel mixture rich. Oil change can help as mentioned above, a worn engine will allow ring bypass and un-burnt fuel residue can find its way into the oil sump and then back up into the intake via PCV system which will enrich the mixture, a fresh oil change can cure this temporarily. If you can get hold of a gas analyser then run the engine up to temp, insert the exhaust probe and let it settle at idle, disconnect the PCV / crankcase ~ rocker cover breathers from intake and see if reading drops. These are the majority of cheap options you can check / try before the cat is replaced. Hopefully your mechanic has a gas analyser. Most MOT testers will try to get the emissions through for a few minutes by revving the motor up anyway as it usually slowly comes down and down within a minute or two with temperature build up, no luck with yours though by sounds of it.

As for "Good" MOT centres, these are hard to come by now as the claws have closed in on rouge MOT stations, it's all got a bit to straight laced these days. I used to have an MOT tester through a friend of a friend and he just wanted car type, Reg number, chassis number, engine number, mileage and £50... Hey-presto.... straight pass everytime! But alas those days are gone and to be fair I'm older now and a bit more strict on myself to keep my cars in good enough nick to pass at a "normal" MOT centre


.

 

[Martin 1]

Please don't give up, don't dump a good car when there are inexpensive possibilities. Do you have the results of the code reading ? Could make a big difference.

 

[Hillsie]

Its worth remembering that the car failed on emissions and isn't unsafe to be on the road

 

[zipdip]

Well the op has spent £800 on the car and it is still a fail,I suggest he does what I said in a earlier post cost about £50 +fuel including the test,I understood what he meant by a good test centre,there is no doubt that test centres do vary a lot,I suppose the ones to avoid are those that line up their people in the morning to salute the flag,over the years I have had a sat nav taken off the screen,incorrect number plate pointed out,a slowly returning seat belt
on the other hand I have seen them not check the brakes,and another not check the lights,not check the seat belts,they will all check the steering and rust and suspension along with the emissions,except the "good " test centres,they are still about,and there is one in the op's locale,but it would be wrong to say which one.

 

[Hillsie]

You're probably right

 

[richard]

Its worth remembering that the car failed on emissions and isn't unsafe to be on the road

Its unsafe for the poor other around him though - in a long term way

 

[Hillsie]

Emission tests are to strict anyway. In a few years they will ban petrol/diesel engines all together

 

[Petrol Pete]

If its failed surely it will be in the 'system' as to why its failed, and that's that. I would try many of the options above before buying a new cat.

Many years ago when emissions were first tested (and not as strict as now) I got an ageing Citroen that had failed badly on emissions through the MOT by removing the air filter emptying a whole can of Wynn's carb cleaner into it and revving the nuts off it.

Passed with flying colours. Maybe not a good plan here though...no carb !

 

[Scott_F]

About 10 years ago, I had a (non Mercedes) car fail its MOT on emissions and thought it might be time for a new catalytic converter. However, a mechanic suggested a bottle of fuel additive (probably about 500 - 750 ml) to be added when the tank was low (less fuel to dilute the additive) but still with sufficient fuel on board to allow the car to be driven 30 miles or so in order to allow the additive to do its job.

It cost about £6 back then and worked a treat - the emissions were fine on the re-test as well as in the half-dozen or more subsequent MOT tests that the car had whilst in my ownership. I can't remember the brand name but there will be various similar products available and it has to be worth a try.

 

[DSM10000]

Emission tests are to strict anyway. In a few years they will ban petrol/diesel engines all together

On what basis do you make such a statement regarding the current test?

If your car had not failed then I imagine you would have a very different and less selfish perspective.