Fail To Pass Emissions

[johnlyckdal]

I recently went to get my car inspected and it failed on emissions. The values are as following:
CO: 5.5 (0.5)
HC: 403 (200)
CO: 2500rpm 1.0 (0.3)
Lambda: 0.74 (0.97-1.03)
Read around for a little while and seems like im running very rich, (hence my poor fuel economy), and most likely need to replace my catalytic converter. Im not so familiar with emissions so im not so sure what causes everything, but 5.5 out of 0.5 is extremely high right. Ive checked the spark plugs and they are OK. Any other thjings to check before I buy a new catalytic converter? Should i look into a new lambda sensor as well?
Previous owner had the car remapped or tuned or whatever after his inspection, and previous values are well within range. Could it be the rich afm thats causing all this, and if so how to fix it.

 

[B5NUT]

I would look into the lambda first. My S2 went from scraping through to an easy pass with just replacing the Lambda. My sensor was 27 years old so was well passed it's best.

 

[johnlyckdal]

I think I found the problem yes, thanks.
By the way, what are the odds that the catalytic converter is shot since it has been runnning like this for the last couple of months.

 

[desertstorm]

That should have put a fault light on the car. I would look to see if somebody has taped over the engine fault light. Check for faults with VAG-COM and see what else maybe faulty. That wiring on the Lamda looks definitely ******.

 

[johnlyckdal]

That should have put a fault light on the car. I would look to see if somebody has taped over the engine fault light. Check for faults with VAG-COM and see what else maybe faulty. That wiring on the Lamda looks definitely ******.

 

[johnlyckdal]

Yeah i scanned it with a good scan tool and no errors codes showed, I think maybe it’s just not performing so well.
Thinking someone has done something to it previously and installed the cable first, and twisted the wires and shielding badly. I’ll get it replaced soon and we’ll see if that’s the fault.

 

[B5NUT]

It looks very burnt around the cable is the flexi leaking?

 

[johnlyckdal]

Not that i could see.
I also discovered something that i was completely unaware of earlier. The car literally doesnt even have a catalytic converter....
A previous owner must have installed a catless downpipe, and there is only one O2/lambda sensor and from what i could tell online theres supposed to be two, I am however missing the second connector. I found a guy doing the same job but had two connectors that split from wires coming from the engine bay, whilst i only have the one, picture below.

Literally no clue where to go from here. I can only assume its had an upgrade to it and the cat removed and sold, and the sensor after the cat removed?
I will finish hooking up the replacement sensor i got tomorrow and try to see if i see a difference in fuel economy, which i think could lead me into the right direction.

side note. I have realised that pretty much all of my forum posts have consisted of me discovering a problem, discussing to myself, and finding the solution. Its just a back and forth discussion between myself pretty much, but i enjoy any comments or input i get

 

[johnlyckdal]

Alrighty, back again
Found a guy selling anaftermarket downpipe with a cat on and only hole for one sensor, he says that he only had the one sensor on his car aswell and that some cars have two.
I think ill buy the downpipe anyways since it wasnt too expensive (150 euro) and try another emissions test to see if i passed.

Now while looking online for downpipes i noticed the quattro and non quattro were different, i am assuming becuase of the driveshaft. How much of a clearance issue would there bere?

 

[hydro s3]

If ur car has no cat on then yes it will definitely fail the mot.
The previous owner has more than likely put a de-cat pipe on and then got the 2nd 02 sensor mapped out.
You could just put a sports cat on and that will pass the mot for you.

 

[johnlyckdal]

If ur car has no cat on then yes it will definitely fail the mot.
The previous owner has more than likely put a de-cat pipe on and then got the 2nd 02 sensor mapped out.
You could just put a sports cat on and that will pass the mot for you.

Yeah seems to be the case. Trying to find a quattro one but they are are to find, only fwd ones. How much do they differ from each other in terms of fitment?

 

[hydro s3]

Audi TT S3 3" Exhaust Down Pipe & De Cat Bypass | eBay

Find many great new & used options and get the best deals for Audi TT S3 3" Exhaust Down Pipe & De Cat Bypass at the best online prices at eBay! Free delivery for many products.

www.ebay.co.uk

This is the downpipe I used.

 

[johnlyckdal]

Audi TT S3 3" Exhaust Down Pipe & De Cat Bypass | eBay

Find many great new & used options and get the best deals for Audi TT S3 3" Exhaust Down Pipe & De Cat Bypass at the best online prices at eBay! Free delivery for many products.

www.ebay.co.uk

This is the downpipe I used.

Yeah i was thinking of just buying the actual catalytic converters and plug the hole. The downpipe splits right under the driveshaft so I was thinking of picking up these from Ebay: https://www.ebay.com/itm/2346973889...DgpzMVMz+82FSNnQXWMgYEfWY=|tkp:Bk9SR4jN6pbqYA

 

[Stuart B]

Lambda 0.75 is default fueling if there's issues with a bunch of sensors egt MAF, EGT, O2... the post cat sensor doesn't impact any fuelling