Failed MOT on emissions

[Coopercupra]

My cupra failed its MOT on too high CO on Idle (all other values were good).
Not sure what it can be, maybe the newly fitted sports CAT wasn't heated up, maybe a small leak in the exhaust, maybe a vacuum leak from the blow off valve and hosing, or maybe I need a o2 spacer.

Any ideas?

 

[Legojon]

My cupra failed its MOT on too high CO on Idle (all other values were good).
Not sure what it can be, maybe the newly fitted sports CAT wasn't heated up, maybe a small leak in the exhaust, maybe a vacuum leak from the blow off valve and hosing, or maybe I need a o2 spacer.

Any ideas?

My MK2 Cupra did the same. I have a Milltek 200 cell cat. What have you got on yours? In the end, the garage mechanics took it in turns for 2 hours burning my car up and down the local country roads. When they pulled it back into the MOT bay, you could literally smell the cat burning and it just about scraped through. I contacted Milltek and apparently they fitted the wrong exhaust and it should have been the HJS version which was fitted (but the cheaper track version was fitted instead). So... I'm not best pleased... and looks like I'll need a new race cat on for December.

 

[Coopercupra]

I have a Scorpion Sports CAT / downpipe.

Could be that it wasn't hot enough

 

[Coopercupra]

Retested today. I made sure the CAT was well warmed up but it failed again


At 2500 rpm the levels were pretty clean. I cant quite figure it out, I first thought it could be the CAT, but i made sure it was hot before the second test and it made no difference. The car is definitely over fuelling / running rich at idle. Could it be the injectors sticking/ leaking?



Very grateful for some help.

 

[BocaBill]

Retested today. I made sure the CAT was well warmed up but it failed again


At 2500 rpm the levels were pretty clean. I cant quite figure it out, I first thought it could be the CAT, but i made sure it was hot before the second test and it made no difference. The car is definitely over fuelling / running rich at idle. Could it be the injectors sticking/ leaking?



Very grateful for some help.

If it's running rich it maybe a bad lost cat O2 sensor, I kept getting EML light every few months with a p0142 code for insufficient burn, Have you checked for any fault codes?
Might be best practice to replace it as you,'ve already done the cat.

 

[Coopercupra]

If it's running rich it maybe a bad lost cat O2 sensor, I kept getting EML light every few months with a p0142 code for insufficient burn, Have you checked for any fault codes?
Might be best practice to replace it as you,'ve already done the cat.

No fault codes

Though I could read any live data from the pre CAT O2 sensor (so could be that). I will try again with different code reader.

 

[Legojon]

Was the sports cat new or used? If it's from new, I'd email Scorpion with test results and see what they say. I'm not best pleased caused I've had my Milltek sports cat 3 years and I'm going to have to replace it before the MOT this year. I pulled the last 3 mot tests and it declined each year until now it won't pass.

 

[Coopercupra]

Was the sports cat new or used? If it's from new, I'd email Scorpion with test results and see what they say. I'm not best pleased caused I've had my Milltek sports cat 3 years and I'm going to have to replace it before the MOT this year. I pulled the last 3 mot tests and it declined each year until now it won't pass.

Oh really!

It was a new CAT

 

[Legojon]

It was CO on idle mine failed on as well.
2017 = 0.15
2018 = 0.277
2019 = 0.31
2020 = 0.45

To me, that looks like a gradual deteration of the catalytic material over the last 4 years.

 

[Coopercupra]

No Fault codes, However the voltage of the 02 Sensor is stuck at 0.47V and I guess it should fluctuate between 0.1 - 0.9 V.

 

[Coopercupra]

Where is the EGR Valve on these engines?

 

[Coopercupra]

Moving forward, I am relying in a ELM OBD plug and the Car Scanner App for the moment.



The app does have an "emissions" diagnose function, normally I wouldn't bother and would rely on codes and live data. But I gave it a try

So these issues match my live data diagnosis of the O2 sensor being stuck at 0.46 V, The air to Fuel creation is 14.65, so that matches that kind of O2 voltage. Digging a bit deeper online, apart from being faulty O2 or a broken ground on the O2 sensor. It could also be a faulty EGR valve. which would match the "emissions test" on the car scanner app.



I am not sure where to find the EGR valve, is it the same as the diverter valve? if it is, I should add i fitted a forge diverter valve, so could be that.

 

[Legojon]

No Fault codes, However the voltage of the 02 Sensor is stuck at 0.47V and I guess it should fluctuate between 0.1 - 0.9 V.

Yes, it should fluctuate between 0.1-0.9V.

Where is the EGR Valve on these engines?

I thought only the diesel Leons have EGRs (Haynes seems to agree with this).

 

[BocaBill]

No Fault codes, However the voltage of the 02 Sensor is stuck at 0.47V and I guess it should fluctuate between 0.1 - 0.9 V.

Mine was stuck on the same voltage when I was trying to diagnose my p0420 code. New post cat 02 sensor sorted it.
For not much money and 10 minute job...it's worth it if it solves it, if not it's 1 less thing it could be

 

[Coopercupra]

Yes, it should fluctuate between 0.1-0.9V.



I thought only the diesel Leons have EGRs (Haynes seems to agree with this).

That will be why I can locate it

I have a forge diverter valve fitted, I will remove that and see if anything changes.

 

[Coopercupra]

Mine was stuck on the same voltage when I was trying to diagnose my p0420 code. New post cat 02 sensor sorted it.
For not much money and 10 minute job...it's worth it if it solves it, if not it's 1 less thing it could be

Agreed! It would be great if it was the after CAT O2 sensor

 

[Coopercupra]

Thread update: Replaced the after CAT O2 sensor tonight. Now I can see the O2 voltage fluctuate between 0.1v and 0.8v, so I guess the old sensor was faulty. I guess 0.46v is default value when the sensor is faulty.

Onto the next issue though... Th engine seems to run on a couple of seconds after the ignition is turned off.

 

[Woody_72]

Does your diag tool display fuel trims? If you're running rich and suspect you have a duff O2 sensor, your fuel trims should reflect it.

 

[Coopercupra]

Does your diag tool display fuel trims? If you're running rich and suspect you have a duff O2 sensor, your fuel trims should reflect it.

I can check the air/fuel ratio, i will check that later.

The O2 sensor was changed yesterday.

I cant understand why the car now runs on for some seconds after IGN is off.

 

[Coopercupra]

All fixed!

New after cat Lamba fitted and Forge diverter valve removed (just in case)

Easily passed the MOT Today