MOT high CO emissions

[fawtytoo]

The MOT tester didn't fail it as it did eventually fall within CO limits (although without any further revving), but was way high on his first try. That wasn't an issue last year. My mechanic suggested 99 octane fuel as the ethanol content is lower and may affect it. The car performs very well so I've no reason to suspect anything wrong. I do about 3,000 miles pa with various driving styles (nothing excessive). It had a service last year which included new spark plugs.

Is this an issue I should be concerned about?

[Carolyn]

Have you got the original cat?  If so, it's probably past its use-by date!

A replacement from Cats2U will sort you out.  They also supply a fixing kit, but the crush gaskets are bobbins. 

[fawtytoo]

Yes, probably the original cat. But wouldn't that be mileage based use-by rather than actual age? The car is 22 years old and done 72,000 miles.

[Carolyn]

They don't last forever.  Mine gave up the ghost around 80,000.

[Alex Knight]

O2 sensor(s) all working as they should be?

That would be my first port of call.

[fawtytoo]

O2 sensor(s) all working as they should be?

One of them is new. I guess I could change the other one regardless.

[Ardent]

Same tester? Same MOT station?
Arrived at MOT with car (cat) up to normal operating temp?

[puma2]

  i once a few years ago  with my yellow 2 got told they struggled with mot with high emission but past it.
so was told may be cat job at the time.

so next year came same place had a conversation with them and it went in just for to look at said problem.
they found the answer it was exhaust leak buy one of the joins they fixed that and no problem since.

[fawtytoo]

Same tester? Same MOT station?
Arrived at MOT with car (cat) up to normal operating temp?

Yeah, same tester and station. I always go for a drive before arriving to get up to temperature.

[fawtytoo]

Someone has suggested to try some cat cleaner. Its that a good idea/make a difference? Or should I resign myself to needing a new cat?

[Carolyn]

I've known Cataclean to help.  As Alex said, it could be an O2 sensor, which can be checked via diagnostic app like Torque Pro (get a decent quality 'dongle' to make the connection).  An exhaust leak is also a possible culprit, as happened with @puma2 . 

All of the above cost time money to sort, but that's kind of the way with these things. You could still end up needing a replacement cat.

Now that was bloody helpful, wasn't it?  

[fawtytoo]

It WAS helpful @Carolyn because it gives me an ordered list of things to check and replace, in cost, low to high.

[fawtytoo]

et a decent quality 'dongle' to make the connection

Can you suggest one please? I have an ELM327 bluetooth dongle for my smart, but I don't know what protocol the OBD is on the MR2.

I do have a dongle with USB but I don't have a laptop anymore.

[Ardent]

Usually work fine with android phones.
Apple phones seem to be a bit finicky in terms of Bluetooth compatibility.

I have a cheap elm327 type dongle works fine with torque pro.

[Joesson]

@fawtytoo

@Carolyn mentions a possible exhaust leak, her " Flappy Stick " could help locate the leak.

NB: A Flappy Stick is a stick with a piece of tissue paper stuck to one end.
With the engine running the tissue is moved around the exhaust system in search of a leak when the tissue will flap.

[Alex Knight]

[Carolyn]

Can you suggest one please? I have an ELM327 bluetooth dongle for my smart, but I don't know what protocol the OBD is on the MR2.

I do have a dongle with USB but I don't have a laptop anymore.

Unless you have a JDM import (MR-S) the protocol is the same as all other Euro OBD.

I had an ELM 327 but I didn't meet with great success with it.  Mind you, I do have a JDM car and that might have had something to do with it.

I ended up getting an 'OBDLink LX' as recommended by @Shazzle.  But it did cost around £50 as I recall.  So try with the one you've got before splashing out.

[fawtytoo]

O2 sensor(s) all working as they should be?

That would be my first port of call.

Well, this is the first and only thing I changed. Both of them from Spark Plugs Ltd. Had an emissions test this morning and all is well.

2 x DENDOX0206 Denso Lambda Sensor DOX-0206
Price: £136.56

[Gaz mr-s]

[2 x DENDOX0206 Denso Lambda Sensor DOX-0206
Price: £136.56
[/quote]

Jesus.....with a little bit of detective work you could get quite a bit cheaper than that.

[fawtytoo]

[2 x DENDOX0206 Denso Lambda Sensor DOX-0206
Price: £136.56


Jesus.....with a little bit of detective work you could get quite a bit cheaper than that.

I couldn't find Denso ones any where cheaper. And they came with the correct connectors.

[Bossworld]

I couldn't find Denso ones any where cheaper. And they came with the correct connectors.

Agreed, I think that's roughly the going rate. Looking at emails, paid £54.86 in June 2020 (Denso 0206). Then £63.64 in October 2023 (Denso 0204).

[BahnStormer]

I recommend investing in the right tools too: 22mm socket with the split down the side for the top two and a decent size 22mm spanner to get around the old one properly as that was a real PAIN until I was able to get a proper spanner on it.

[The Other Stu]

I recommend investing in the right tools too: 22mm socket with the split down the side for the top two and a decent size 22mm spanner to get around the old one properly as that was a real PAIN until I was able to get a proper spanner on it.

Proper O2 socket was about £8 from Amazon. I've had it years. Definitely one to have in.

[The Other Stu]

I got chatting to the owner at a new place I've started using today after the MOT.
He confirmed that most CO problems are holes in exhausts or loose fitting manifolds.

Lambda is often a bad sensor or a poorly cat.

In my case, I have a tiny bean-tin 100 cel cat. Got it properly warm, it went through. Albeit on the edge, but a pass is a pass. It was actually great to have a tester who was happy to do the legwork to get it really hot.

In fairness, he said he absolutely loved driving my car and it put a smile on his face. I forgot to warn him that it was a 2ZZ  he found it out by accident pushing it towards the redline.

[fawtytoo]

a decent size 22mm spanner

I bought one but where is the 3rd sensor? Is it on/near the cat? Do I need to remove anything to get to it?