MOT fail- emissions
Discussion
Hi guys,
We took me wife's 2008 R56 Mini Cooper for its MOT yesterday and much to our surpise it failed quite badly on emissions. The test results were as follows:
So, lambda looks fine on all tests. What I'm confused about is how the CO and HC can be fine on some tests but fail badly on others? I would have thought if there was a problem then it would be a little more consistent?
Something worth mentioning is that the printout states the engine speed for the test has been controlled manually, presumably using the accelerator. I've got no issue with this but it was also put as an advisory "Emissions erratic, maintaining revs tricky". I took the car out for a spin last night and there are no issues with holding the revs constant at all, idle is very constant and the car feels to be running absolutely fine. There is no smoke or smell either.
I'm happy to get work done if it needs it but I don't want to get the cat replaced for example if it's purely down to a bad test. I do trust this MOT centre as I've used them for years but I've got another one I can use if need be.
Any advice welcome. Cheers!
We took me wife's 2008 R56 Mini Cooper for its MOT yesterday and much to our surpise it failed quite badly on emissions. The test results were as follows:
| Test | CO (max) | HC (max) | Lambda (max) |
|---|---|---|---|
| Fast Idle 1 | 0.66 (0.2) | 66 (200) | 0.982 (1.03) |
| Fast Idle 2 | 0.17 (0.2) | 342 (200) | 0.984 (1.03) |
| Natural Idle | 0.15 (0.2) | - | - |
So, lambda looks fine on all tests. What I'm confused about is how the CO and HC can be fine on some tests but fail badly on others? I would have thought if there was a problem then it would be a little more consistent?
Something worth mentioning is that the printout states the engine speed for the test has been controlled manually, presumably using the accelerator. I've got no issue with this but it was also put as an advisory "Emissions erratic, maintaining revs tricky". I took the car out for a spin last night and there are no issues with holding the revs constant at all, idle is very constant and the car feels to be running absolutely fine. There is no smoke or smell either.
I'm happy to get work done if it needs it but I don't want to get the cat replaced for example if it's purely down to a bad test. I do trust this MOT centre as I've used them for years but I've got another one I can use if need be.
Any advice welcome. Cheers!
dlockhart said:
just a thought have you tried warming the car up (i.e 10 mile trip) before going to the MOT center, that way the autochoke and electronic management of the engine would not interfere with the revs.
Thanks, the garage did say that they made sure it was warm first but I'm not sure quite how warm. We dropped the car off at 8:30 at which point it had a service including oil and coolant change. The time on the MOT was 11:27 but I'm obviously not sure how long it was between the service and the MOT.The other thing that the certificate said was "Engine oil temperature check: Temperate gauge showed warm engine". That's a pretty neat trick seeing as the car doesn't have a termeprature gauge!
I'm inclined to think the engine wasn't up to temperature and the revs weren't being held correctly, rather than there is a fault with the car?
trickywoo said:
I don't think your lambda is OK it should read 1.00 or 0.01 either way.
Before going too mad with other things I'd put a new O2 sensor on it.
The min/max for lambda on the sheet says 0.970-1.030, so I think 0.984 should be okay? Seems to be pretty much bang in the middle of the range.Before going too mad with other things I'd put a new O2 sensor on it.
JustADay said:
The min/max for lambda on the sheet says 0.970-1.030, so I think 0.984 should be okay? Seems to be pretty much bang in the middle of the range.
Despite showing a range I'm pretty sure the 'correct' value should be 1.00. Your reading is quite a bit off which is likely to be either O2 or MAF sensor.O2 sensors tend to be cheaper, if not always easier, to replace than MAF.
I had a similar issue with my 328i
A pair of new lambdas and a long blast on the motorway (Getting off and back on etc, using low gears pulling all the way to redline and cruising in 4th instead of 5th) cured my issues and the emissions were lower than the previous year.
Now every year my car goes for MOT I take it for a 30min motorway drive to make sure it's all warm and cleared out
A pair of new lambdas and a long blast on the motorway (Getting off and back on etc, using low gears pulling all the way to redline and cruising in 4th instead of 5th) cured my issues and the emissions were lower than the previous year.
Now every year my car goes for MOT I take it for a 30min motorway drive to make sure it's all warm and cleared out
JustADay said:
I'm inclined to think the engine wasn't up to temperature and the revs weren't being held correctly, rather than there is a fault with the car?
They did the basic emissions test, which it failed which led to a vehicle specific test. The second test has a 3 minute section where the engine is held at 2500 to 3000rpm, this along with the first test and the remainder of the second test would make it hot enough.How much oil does the engine use?
mcford said:
They did the basic emissions test, which it failed which led to a vehicle specific test. The second test has a 3 minute section where the engine is held at 2500 to 3000rpm, this along with the first test and the remainder of the second test would make it hot enough.
How much oil does the engine use?
I would guess around 500ml/ 1,000 miles. More than I would like but in spec and as much as it's ever used, and this is the first time it's ever come close to failing on emissions.How much oil does the engine use?
Do you think this could be related then?
dlockhart said:
just a thought have you tried warming the car up (i.e 10 mile trip) before going to the MOT center, that way the autochoke and electronic management of the engine would not interfere with the revs.
+1 for trying a proper drive before it is tested. Get some heat into the cat.I had a car fail on the emissions years ago. The tester reluctantly agreed to retest it after I went for a short hoon.
"it wont make any difference" and "you're wasting your time" etc.
Short hoon + retest = pass
I tried Cataclean on a 1.8 Freelander that seemed to delight in producing wafty emissions results. Not really any difference to any of the readings in my experience aside from leaving you £17 out of pocket. Best method was a good 20 minute run up and down the local B-Roads to get everything hot - many of the emissions control systems on modern engines don't really work until they are thoroughly warmed up. It may be worth giving the catalytic converter a quick tap to see if it rattles - if so then it may just be that you need a new cat.
My first suspicion would be rich running (high HC and incomplete combustion/high CO) - so it's possibly putting too much fuel in (can be result of skewed temp sensors making the engine think it's colder than it actually is / iffy lambda sensors). It could also be something simple like restricted airflow (is the air filter dirty or due for renewal) - so the engine isn't getting enough air to completely burn off all of the fuel.
Does the car smell of petrol when it's run for the first couple of minutes in the morning? Don't go sniffing the exhaust for obvious reasons - but you can sometimes get a whiff of petrol fumes from the tailpipe if there is a case of rich running.
Other candidate could be poor ignition/spark - possibly a jippy coil pack/spark plug that isn't igniting the fuel mixture as it should. You would possibly notice symptoms like a misfire and/or EML light flashing, etc. if it were a bad spark - so I'd look at the fuelling side of things first.
My first suspicion would be rich running (high HC and incomplete combustion/high CO) - so it's possibly putting too much fuel in (can be result of skewed temp sensors making the engine think it's colder than it actually is / iffy lambda sensors). It could also be something simple like restricted airflow (is the air filter dirty or due for renewal) - so the engine isn't getting enough air to completely burn off all of the fuel.
Does the car smell of petrol when it's run for the first couple of minutes in the morning? Don't go sniffing the exhaust for obvious reasons - but you can sometimes get a whiff of petrol fumes from the tailpipe if there is a case of rich running.
Other candidate could be poor ignition/spark - possibly a jippy coil pack/spark plug that isn't igniting the fuel mixture as it should. You would possibly notice symptoms like a misfire and/or EML light flashing, etc. if it were a bad spark - so I'd look at the fuelling side of things first.
LandRoverManiac said:
I tried Cataclean on a 1.8 Freelander that seemed to delight in producing wafty emissions results. Not really any difference to any of the readings in my experience aside from leaving you £17 out of pocket. Best method was a good 20 minute run up and down the local B-Roads to get everything hot - many of the emissions control systems on modern engines don't really work until they are thoroughly warmed up. It may be worth giving the catalytic converter a quick tap to see if it rattles - if so then it may just be that you need a new cat.
My first suspicion would be rich running (high HC and incomplete combustion/high CO) - so it's possibly putting too much fuel in (can be result of skewed temp sensors making the engine think it's colder than it actually is / iffy lambda sensors). It could also be something simple like restricted airflow (is the air filter dirty or due for renewal) - so the engine isn't getting enough air to completely burn off all of the fuel.
Does the car smell of petrol when it's run for the first couple of minutes in the morning? Don't go sniffing the exhaust for obvious reasons - but you can sometimes get a whiff of petrol fumes from the tailpipe if there is a case of rich running.
Other candidate could be poor ignition/spark - possibly a jippy coil pack/spark plug that isn't igniting the fuel mixture as it should. You would possibly notice symptoms like a misfire and/or EML light flashing, etc. if it were a bad spark - so I'd look at the fuelling side of things first.
No smell of petrol at startup at all, everything seems to be running fine. I took a look at the service history last night and the plugs were changed about 20k miles ago so I don't think they should be gone yet, might be worth a look though. I did change the air filter last night though as is was pretty much jet black- doesn't fill you will confidence on main dealer servicing!My first suspicion would be rich running (high HC and incomplete combustion/high CO) - so it's possibly putting too much fuel in (can be result of skewed temp sensors making the engine think it's colder than it actually is / iffy lambda sensors). It could also be something simple like restricted airflow (is the air filter dirty or due for renewal) - so the engine isn't getting enough air to completely burn off all of the fuel.
Does the car smell of petrol when it's run for the first couple of minutes in the morning? Don't go sniffing the exhaust for obvious reasons - but you can sometimes get a whiff of petrol fumes from the tailpipe if there is a case of rich running.
Other candidate could be poor ignition/spark - possibly a jippy coil pack/spark plug that isn't igniting the fuel mixture as it should. You would possibly notice symptoms like a misfire and/or EML light flashing, etc. if it were a bad spark - so I'd look at the fuelling side of things first.
We're taking it in for a new MOT at a different garage this afternoon and I will make sure we get it nice and hot on the way. It won't be sitting around for a few hours before the test either so if it doesn't pass this time there's obviously something a bit more serious wrong.
I'll update you later!
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