Failed MOT on Emissions - What could be the problem?

[vincent81]

Hi, hoping someone can help with the following. Had my BMW E93 (2007) fail it’s MOT at Halfords due to high emissions. The car’s just over 11 years old and only does a few thousand miles each year (mostly short journeys). It’s done just over 3,000 miles since its MOT last year and then it passed the emissions test with flying colours.

Repair immediately (major defects)
- Exhaust carbon monoxide content after 2nd fast idle exceeds default limits [8.2.1.2(b)]
- Engine mil inoperative or indicates a malfunction [8.2.1.2 (h)]

Although not sure why it’s failed on mil inoperative? As there are no warning lights on on the dashboard.



I have sometimes noticed the smell of petrol/burning from the exhaust, so not sure if this could be related to the above?

The guy at Halfords did say if you use it mainly for short journeys then it’s worth getting Cataclean and taking it for a ride up the motorway. Would that help? Alternatively what else could be the cause of the problem and how can I rectify it?

Thanks in advance.

[jsims1]

There won't be any engine light showing up on the dashboard because it doesn't work.
Sometimes a good Italian tune-up can work well on emissions as stated so go for that for the emissions then you need to find out why your EML doesn't work.

[Welshbeef]

OP a spirited drive is certainly required ie the exhaust tinking after the drive when it’s cooling down on the drive.

Use it between 5,000-7000 revs for a period of time ie you’ll get it very hot and that will help dislodge the carbon build up.


When you took it for the MOT was the engine up to operating temp?

[M4cruiser]

That's weird, because the natural idle is ok but the fast idle is way way out.
The idle valve seems to be working, but when you add some throttle the fuel isn't burning properly.
Or the cat's done for.
Not sure myself.

[vincent81]

Welshbeef said:

When you took it for the MOT was the engine up to operating temp?

Nope. The Halford's branch is barley a 30 second drive from where I live.

[Colonel D]

the most common causes would be, small pin hole leak along the exhaust somewhere, lambda sensor (starting to go bad so no light shows), or cat is braking/broken

[spookly]

If the EML is shot it might be masking a fault that effects emissions that you could discover with a OBD2 code reader.
Could be something like the O2 sensor. Try getting any fault codes read.

[Welshbeef]

vincent81 said:

Welshbeef said:

When you took it for the MOT was the engine up to operating temp?

Nope. The Halford's branch is barley a 30 second drive from where I live.

This is the problem.
Always have a drive so it’s fully up to temp before you go for a test. Test shouldn’t be conducted whilst it’s in effect on choke

[oldaudi]

My Golf TDi failed with emission issues. Garage is a few 100 yards from where I live and they started the MOT as I was walking out of the garage. Car was way too cold. I knew it failed as I was refreshing the MOT page online as soon as I was at work. The called me to say that it had failed but confident that they could get it through the MOT just by warming it up. I imagine they did a coffee run or a bacon roll run in it because a few hours later it had passed without troubleshooting or replacing parts. They just need to be hot. Obviously there could be other issues but ensure the temp is good

[stevieturbo]

vincent81 said:

Nope. The Halford's branch is barley a 30 second drive from where I live.

they should not be performing the test unless the engine is fully warmed up.

[dhutch]

They should certainly have got it up to operating temp.

If you can do a blast down a motorway for half an hour (?) and then make sure it's got going it it's well worth a shot, if you don't want to keep mithering them any other garage will do you an emissions test if you ask and pay.

[vincent81]

How would they establish if the EML light is not working? I'm assuming it would only be lit up if there was a fault.

[GreenV8S]

vincent81 said:

How would they establish if the EML light is not working? I'm assuming it would only be lit up if there was a fault.

It should normally come on with the ignition and go out when the engine is started.

[anonymous-user]

High co2 suggests a knackered cat.

[stevesingo]

I don't see a CO2 reading, only CO. Lambda id 0.955, which is rich, this would give high CO reading. Why it is rich is the question. The ECU should aim to maintain Lambda 1 at light load, so one would assume that the ECU believes it is Lambda 1. I would suggest that the Lambda sensor kaput.

OP, what engine?

[thebraketester]

Thesprucegoose said:

High co**** suggests a knackered cat.

Edit****



Pretty much.

My car (2007 GTI Edition 30) failed its MOT this year on high emissions. Its got a 200CEL cat and I presume its nearing the end of its life.

I took it back to the MOT tester later the same day having given it a good kick in and even then he had to stand on the pedal for 5 minutes to get it to pass, and it only just passed at .20% .

New cat time....

[vincent81]

stevesingo said:

I don't see a CO2 reading, only CO. Lambda id 0.955, which is rich, this would give high CO reading. Why it is rich is the question. The ECU should aim to maintain Lambda 1 at light load, so one would assume that the ECU believes it is Lambda 1. I would suggest that the Lambda sensor kaput.

OP, what engine?

Engine is 1995 cc

[anonymous-user]

stevesingo said:

which is rich, this would give high CO reading. Why it is rich is the question.

Lean and rich can both occur at same time, so confusing terms.

A faulty maf may also be the culprit, disconnect see the readings again.

[vincent81]

GreenV8S said:

vincent81 said:

How would they establish if the EML light is not working? I'm assuming it would only be lit up if there was a fault.

It should normally come on with the ignition and go out when the engine is started.

That appears to be working fine. With keys in the ignition & pressing the Start button (no foot on the pedal so engine has not yet been started) the EML light shows up on the dash (as per the picture below). And on actually starting the engine it goes away.

[bmwmike]

Is this an n43 ? Could it be a leaking injector?