Another High CO Emissions Thread!

matthewobrn

Hi emissions specialists!

I have a MK5 Golf 2008 TSI 140hp 219k on the clock.

I don't think it burns oil, maybe 1-2 ltr per year. I'm lead to believe this is well within acceptable limits.

There is not black soot on the back of the car and it does 50% motorway 50% city miles.

I have been plagued with emission problems for each nct since buying the car 2 years ago.

Last year I used a company to clean the intake and exhaust system. It was called Terra Clean and it worked in passing the NCT.

2022 Fail:

2022 Pass:

I tried it again this year with no luck.

Here is the latest NCT results 2023 Fail:

Please let me know your thoughts.

There is only one error being thrown by the ecu that I checked using VCDS:

008196 - Intake Manifold Flap; Bank 1

P2004 - 000 - Stuck Open

I'm leaning towards the CAT but want some feedback before the investment.

Thanks in advance.

Matt

mk7r

Your cat is buggered

matthewobrn

Thought so.

Any recommendations for after market cats?

Hellrazer

Id be checking exhaust first for holes before going for a Cat.

High CO with lambda within the right limits would point me towards an exhaust leak BEFORE the CAT or O2 sensor. That and the fact it passed on idle.

Ive seen manifolds cracked on these before.

mk7r

https://www.boards.ie/discussion/comment/121291762#Comment_121291762

This is some sage advice to check out, I missed the low idle pass this year so definitely do check out the exhaust between the head and O2 sensor 1

Hellrazer

https://www.boards.ie/discussion/comment/121291795#Comment_121291795

I remember a very old mechanic friend of mine who passed away a few years back gave me a hand written list of the NCT fails on emissions ie High CO /high idle with normal lambda = exhaust leak before cat. High CO at high idle with high lambda = exhaust leak after cat. High lambda = misfire running too rich etc. Low lambda /High CO - usually a cat. High HCs - usually a cat not doing its job.

That list served me well. I must see if I can find it and upload a copy of it here. Not always 100% right but always gave me a good place to start.

mk7r

https://www.boards.ie/discussion/comment/121292928#Comment_121292928

I wouldn't look too hard for the list 😅

The only job of the cat is to reduce the CO it doesn't affect the HC, that would be more like a bad spark plug, misfire, poor compression etc.

The high CO at high idle and passing at low can be due to a crack but it also can still be the cat as the volume of gas is much higher at high idle and it may not have the capacity to covert that much CO

The cat also can't affect the lambda value as it's behind it so high CO low lambda can't be the cat.

Rich is low lambda and lean is high lambda so you might have those two swapped around

ofcork

This is my work colleague fail this morning opinions?

matthewobrn

https://www.boards.ie/discussion/comment/121291762#Comment_121291762

Thanks for the advice, I will check for a leak pre cat.

This would suggest an exhaust leak in the engine bay. Either manifold of post turbo.

Would I not be able to smell the fumes in the car if this is the case?

matthewobrn

https://www.boards.ie/discussion/comment/121291795#Comment_121291795

O2 Sensor 1 is in the Cat assembly (before the honeycomb). Not a lot of places to look for the leak.

matthewobrn

Thanks for the responses, anyone know where to get a reliable after market CAT?

matthewobrn

https://www.boards.ie/discussion/comment/121294026#Comment_121294026

What car is it?

ofcork

08 peugeot 308.