[Dipsd]

Had the car a year and second owner. Took it in for MOT a few days ago and the guy said it was due to the lamber sensor I think.

Said the car was being driven 'like a pussy'. He said it was something to do with changing the gear too soon so something was getting blocked so the car was failing one of the emission tests that gets printed out.

So he took the car out for a spin to get it going and said it got closer to passing on second attempt. Didn't work so same was done again and THEN it passed.

He came and told me after the second fail and I told him to do what he needed to as he felt bad about flooring someone else's car. It's only a 320 so I knew it wasn't just for the fun! And he's a family friend for a few years so he was doing all he could to help.

Anyone heard of this issue before? The MOT cost me £70 in the end.

[toxicnerve]

I thought the Lambda sensor just measures the Oxygen content of exhaust? I guess if it's knackered and your engine is burning fuel properly it could affect your emissions (thinking about it, it would).

The only thing thing that can become blocked is the DPF...is yours a diesel?

The fact that he took it for a drive (did he thrash it?) sounds like he either managed to get the DPF to regenerate but I can't see how that would affect the emissions test, I thought it only checked for gases not particulates?

The only other thing is that by driving it (possibly hard) he got the cats up to temp so they were working more efficiently and therefore the emissions results were better the 2nd and 3rd times???

[ddogg35]

Originally Posted by toxicnerve

The only other thing is that by driving it (possibly hard) he got the cats up to temp so they were working more efficiently and therefore the emissions results were better the 2nd and 3rd times???

this seem the most logical answer to me
mind you i have heard of engines not performing as well if they are babied and that a good thrash could get it performing normally again

[Dipsd]

Originally Posted by toxicnerve

The only other thing is that by driving it (possibly hard) he got the cats up to temp so they were working more efficiently and therefore the emissions results were better the 2nd and 3rd times???

This is exactly what he said. He said a few other things too so I got confused.

Will this cost me in the long run? How much am I looking at? Sadly I didn't extend the warranty.

[toxicnerve]

No idea how much cats are so I can't help with that. Do you have a car that has passed MOT at the moment?

If so I'd not worry about it too much and spend a bit of time researching/getting quotes before getting ahead of yourself. Obviously main dealer prices will be more than an independent so worth shopping around.

A duff cat won't affect the running of the car, it will just mean your motor is putting out more of the nasty stuff from the exhaust. This is a problem that needs sorting but it's not what I would class as "priority 1".

Also, it's not uncommon for people to remove cats on their cars. Particularly when a car has primary and secondary cats some people choose to remove one. Then, when going for MOT they just make sure they go on a decent run/thrash the tits off it before turning up to the test station so the remaining cat is smoking hot and performing optimally!

[atariboy]

My 320i had an engine warning light come on and when I took it in, I was told that it was a sensor in the exhaust that was sooted up. They reset the sensor and advised me to take a long hard blast down the motorway at least once a month to keep it clear.
I guess it reinforces the fact that BMW's are designed to be driven and not used for pottering around town.

[toxicnerve]

It applies to most (if not all I.C.E.) cars. Short journeys are terrible for efficiency and engine health.

During short journeys the engine/ancillary systems never gets up to temperature. Combustion is not optimal, the cats are not performing efficiently and even the DPF will never get a chance to regenerate.

The other thing to consider is that other fluids, for example differential and gearbox oil will also never get up to temperature either.

[Dipsd]

Originally Posted by atariboy

My 320i had an engine warning light come on and when I took it in, I was told that it was a sensor in the exhaust that was sooted up. They reset the sensor and advised me to take a long hard blast down the motorway at least once a month to keep it clear.
I guess it reinforces the fact that BMW's are designed to be driven and not used for pottering around town.

Yeah, this is pretty much what I was told but without the warning light coming on.

@Toxicnerve - Yeah, the guy got my BMW to pass the MOT in the end so everything is ok for now. I'm just glad I didn't take it to an AUC otherwise I'm sure they would have got me to bend over straight away instead of trying to get the car to pass.

My brake fluid change has been due for a month, that wouldn't affect this would it?

[jrah]

My dads 57 318i had the same problem, it failed its emissions test in february. To fix the problem a BMW technician drove it along the M40 at "motorway cruising speed" for 40 minutes to clean out the injectors it then passed it's emissions test

[parapaul]

Originally Posted by Dipsd

My brake fluid change has been due for a month, that wouldn't affect this would it?

No

[Dr Dave]

It's known in the trade as an Italian Tune Up.

The catalysts and exhaust sensors need to get up to a high working temperature to function correctly - with a car that only does short trips and is babied around, this ain't gonna happen.

Think yourself lucky you didn't get pulled up at a roadside emissions check!

[toxicnerve]

Originally Posted by Dr Dave

It's known in the trade as an Italian Tune Up.

The catalysts and exhaust sensors need to get up to a high working temperature to function correctly - with a car that only does short trips and is babied around, this ain't gonna happen.

Think yourself lucky you didn't get pulled up at a roadside emissions check!

Do they do that?

[Dr Dave]

Well they certainly did around these parts - big layby and signage "Vehicle roadside emissions testing"

Not seen them for a year or two, probably got axed.

[Dr Dave]

Click here for more info, it still happens by the looks of it

VOSA Roadside Emissions Testing

[Dipsd]

Strange. I did about 200 miles 3 days before the MOT at 80-90mph all the way.

Anyway, I learnt a lot in this thread, thanks guys!

[JonnySi]

Its because the N43 direct injection engine runs so lean that it actually produces other harmful emissions. One of these is NOx, which is mainly emmited from diesels. A petrol MOT gas meter will see this as a fail because the CO is also too high. By driving the vehicle hard, the engine changes and runs in homogenous charge mode (like a normal petrol) and these harmful emissions drop and pass the MOT.

[Dipsd]

That sounds like the technical explanation to what BMW gave me.

I went for my brake fluid change and asked when I was paying. They said plenty of people who go to non AUC garages for MOTs ask about it. It's to do with the config of the garage's system which doesn't recognise everything the BMW throws out so fails it. It's not a problem on the car, it's a problem with the garage's equipment.

[Bee Pee]

Methinks this is an old school issue, coined by the phrase - "blowing the carbon out" or "giving it decoke w/o taking the cylinder head off".

Had a similar issue years ago with my Golf VR6. Took an expat job overseas, rotation 90 days in 2 weeks off. Left my golf with my folks. Someone rear ended my mum's 205 GTI 1.9 so whilst she was waiting for the coroner to confirm her Pug was a write-off she tooled about in my golf. She liked it so she trousered her write-off money and continued on using my VR6 as if it were hers.

Came back on home leave and took the car for MOT. Tick over was a tad errantic but thought nowt of it until tester man said my car had flunked on the emissions. He said bring it back within the hour and he will re-check it.

Spent the next hour in mainly 3rd & 4th buried in the upper echelons of the rev range. Tough messy job but hey I had to do it. Idling as sweet as a nut, returned to tester man and sailed thru the emissions and OK'd MOT-wise.

Lesson learnt to make a point of thrutching my cars regularly incl the eve before MOT day ever since. Moreso with my e91 to fend off the valve crust buildup its direct injection N54 are known for.