MOT advice - Emissions

[OliSmith175]

I know this has been done to death and covered many times, but...

I had my BMW E36 M3 in for an MOT last year and it failed on:

Exhaust Lambda reading after 2nd fast idle outside specified limits (8.2.1.2 (c))
Exhaust carbon monoxide content after 2nd fast idle exceeds manufacturer's specified limits (8.2.1.2 (a))
Nearside Rear Parking brake efficiency below requirements (1.4.2 (a) (i))
Nearside Rear Inner Suspension component mounting prescribed area excessively corroded significantly reducing structural strength (5.3.6 (a) (i))
Offside Rear Inner Suspension component mounting prescribed area excessively corroded significantly reducing structural strength (5.3.6 (a) (i))
Offside Front Inner Integral body structure corroded to the extent that the rigidity of the assembly is significantly reduced ( floor at jacking point ) (6.1.1 (c) (i))

As per my thread in 'Reader's cars' I've sorted the corrosion and the parking brake.

I've also made an effort to try and sort the emissions. The exhaust manifold had a small cut (looks like where someone has used an angle grinder to remove a bolt, but caught the manifold) which I've welded up. I've also replaced the O2/lambda sensors (this car has two pre-cat sensors) with brand new Bosch sensors and I've removed the aftermarket Scorpion exhaust back box (which had cracks around the hanger brackets so was probably leaking) with the original back box. I was hoping that a combination of the leaking manifold and (I believe) original O2 sensors are what were causing the emissions to be out, but I'm still a little cautious.

I've read on the forums several people saying these cars regularly fail on emissions and to give it a good run before the MOT to warm up the cat. Problem is, the MOT garage that I am using is literally 0.1 mile up the road, so short of illegally (no MOT or tax) taking it for a long drive before the MOT, I don't have any way of warming up the car properly.

Any advice on how to get around this? I assume having it idling for 30+ minutes won't be enough to warm up the cat? Maybe a silly suggestion, but what about having the car idle to warm the engine up, then jacking it up and heating up the cat with a blow torch just before taking it in? Do I risk damaging the cat if I do this?

Just to add - the engine, exhaust, cat is all original, serviced regularly (although it's been off the road for a few years). It had a genuine BMW air filter and new spark plugs about 2500 miles ago.

[CrutyRammers]

Idling won't, but running it at a few thousand rpm for 5-10 mins or so will. The garage should really do this to get it up to temp before testing. Otherwise, I wouldn't worry, just take it for a quick 10 minutes up the road. You are on your way to the MOT, you'd have to be incredibly unlucky to be stopped and charged for that.
Compared to the risks of using a blowtorch on the underside of your car with all the fuel and brake lines, and flammable sealant, it's a no-brainer.

[Pastor Of Muppets]

There is also the problem of the MOT station having the car sat there cooling down before they get round to it.

What about booking it in to a station that is further away so you can get it properly up to temperature?

[OliSmith175]

I had considered that, but I like the local garage - they're a small business but are very honest and fair so I like to throw the business their way. They did say that so long as they're not already doing a car when I arrive they will MOT it straight away and I was planning on taking it first thing in the morning.

I might have a drive to the local shell (about 5ish minutes away each way) and put some V Power in it before the MOT but just hold it in a low gear all the way to put some heat into the car.

[montyjohn]

I had an MX5 that used to be really hard to get through emissions.
I used to warn the MOT center when I rocked up and they were quite happy to try the test a few times to get it through.
One garage even took the car for a quick blast (I assume they put trade plates on?) right before the test.

So it might help to warn the garage before hand.

[CrutyRammers]

Again, they should be getting it up to temp anyway:

https://www.gov.uk/guidance/mot-inspection-manual-...

Basic emissions test
Ensure a daily leak test has been carried out.
Make sure the engine is hot. If the engine is not hot, raise the engine speed to between 2,000rpm and 3,000rpm until it’s up to normal operating temperature.
You can tell that the engine is hot from any of the following:

the temperature gauge
the cooling fan has cut in
the cooling hoses are hot
To do the emissions test:

[OliSmith175]

CrutyRammers said:

Again, they should be getting it up to temp anyway:

https://www.gov.uk/guidance/mot-inspection-manual-...

Basic emissions test
Ensure a daily leak test has been carried out.
Make sure the engine is hot. If the engine is not hot, raise the engine speed to between 2,000rpm and 3,000rpm until it’s up to normal operating temperature.
You can tell that the engine is hot from any of the following:

the temperature gauge
the cooling fan has cut in
the cooling hoses are hot
To do the emissions test:

But as you mentioned in your first reply, simply idling the engine won't get the catalytic converter up to temp. What you have quoted here states the temp. gauge only has to show the engine is up to temp, which would be achieved just by idling.

I have advised the garage that I'd like them to do emissions first, as it failed on emissions last year. I'll be staying with the car whilst they do the testing too, so I'll ask them to have a go a couple of times if it's not playing ball. I did also read online that having the rpm at the lower end of the fast idle (ie closer to 2,500rpm rather than 3,000rpm) can make quite a big difference to the results, so I'll ask that they do that also.

Edit to add: it's booked in for tomorrow morning... wish me luck!

[CrutyRammers]

OliSmith175 said:

CrutyRammers said:

Again, they should be getting it up to temp anyway:

https://www.gov.uk/guidance/mot-inspection-manual-...

Basic emissions test
Ensure a daily leak test has been carried out.
Make sure the engine is hot. If the engine is not hot, raise the engine speed to between 2,000rpm and 3,000rpm until it’s up to normal operating temperature.
You can tell that the engine is hot from any of the following:

the temperature gauge
the cooling fan has cut in
the cooling hoses are hot
To do the emissions test:

But as you mentioned in your first reply, simply idling the engine won't get the catalytic converter up to temp. What you have quoted here states the temp. gauge only has to show the engine is up to temp, which would be achieved just by idling.

I have advised the garage that I'd like them to do emissions first, as it failed on emissions last year. I'll be staying with the car whilst they do the testing too, so I'll ask them to have a go a couple of times if it's not playing ball. I did also read online that having the rpm at the lower end of the fast idle (ie closer to 2,500rpm rather than 3,000rpm) can make quite a big difference to the results, so I'll ask that they do that also.

Edit to add: it's booked in for tomorrow morning... wish me luck!

I CBA to argue, but no tester or mechanic is going to think that getting a car to working temp means "leave it idling for a bit." . It means "2-3K for several minutes until the fan comes on", and has done since the year dot. Good luck anyway.

[brillomaster]

Sure, the MOT garage is only a stones throw away, but... didnt you hear something about that bit of road being closed tomorrow? best take the long way round - you know, just in case.

oh actually - doesnt the car run real bad unless you fill it up with esso/vpower/tesco momentum? (delete to leave whichever is furthest away)

[OliSmith175]

CrutyRammers said:

I CBA to argue, but no tester or mechanic is going to think that getting a car to working temp means "leave it idling for a bit." . It means "2-3K for several minutes until the fan comes on", and has done since the year dot. Good luck anyway.

Genuinely wasn’t trying to argue, apologies if it came across that way. Just that to me it reads that the .gov guidance advises that the engine be hot which can be measured by either the temp. gauge (presumably being in the normal operating temperature range), hot coolant pipe, or the rad fan kicking in. All things that would happen from idling for long enough (30+ minutes). Granted it does mention about increasing rpm if the engine is not up to temp, but I read that as only being if the engine is not yet up to operating temperature. There’s no mention that I can see of ensuring the catalytic converter is up to temperature.

Thanks for the advice though all. Hopefully it will be fine with a quick run to the fuel station. I’ll make sure coolant and oil is up to temp before setting off so I can keep the rpm high.

[paintman]

Been discussed many many times and from those discussions AFAIAA there is nothing that says how far you are allowed to travel to attend a pre-booked MOT.
Insurance is a must.

I take ours for a quick blast up & down a short length of dual carriageway which starts less than a mile from my house & then to the garage.

Edited by paintman on Monday 8th November 18:43