1.4TSI Emissions failure, suspected ECU trickery?

[Kyleo95]

Hi all,

I'm having an issue with the emissions of my 1.4tsi Scirocco 2015 with a czc engine (just over 50,000 miles) and was wondering if anyone had any further insight or if something similar has happened to them.

The emissions failed the UK MOT test with readings for fast idle of;
CO - 1.78% (max 0.3%)
HC - 126ppm (max 200ppm)
Lambda - 0.947 (0.97min, 1.03max)

I suspected emissions could be an issue as there is a noticeably strong smell whenever walking around the car when it is running, although there is no engine light warning.
I took the car to a fuel injection specialist for diagnostics where they found no stored faults, and live data is supporting the rich mixture suggesting that the sensors are working as normal.
I have only been doing short drives this year so carbon build up was suspected (makes sense with direct injection). They took the car for a drive at high RPM and did a retest and the emissions were almost halved. I thought we were finally getting somewhere at this stage.
The garage then added a fuel additive to help lower this a bit further and took the car on 20 minute drive. After a quick retest with just the emissions hose connected to the exhaust the CO was around 2.6%! This is when things got very strange. The bonnet was then opened and the emissions dropped significantly with CO at 0.32%...

With keeping the bonnet open and gradual rpm increase to fast idle , the mechanics could then get perfect emission results - CO = 0.03%, HC = 12ppm and lambda at 1.00.

Although some of the issue appears to be from carbon build up in the manifold, I've been told that the main problem stems from the ECU that once the bonnet is closed the CO emissions increases roughly 8 times the amount.
The garage (independent) says that there is a ECU recall available for this engine. Although it specifies that it is to improve battery/power management and notes nothing on emissions, they believe that there may be some other update included which could solve this issue.
If it is an ecu software issue I don't understand how this hasn't been a problem from day 1.

This seems oddly similar to VWs emissions problems but there doesn't seem to be any relation to their petrol engines...

It would be great to know if anyone has experienced something similar to this and any advice would be greatly appreciated. If not, I hope this topic might help others in their diagnostic!

[Kyleo95]

Thought I would provide an update to anyone experiencing the same issue.

I got the ECU update today at the VW dealership and the emissions dropped immediately and significantly.
CO now reading 0.00%
HC at 1ppm
Lambda - 1.01

I'm still very unsure at how the software could have suddenly caused such poor emissions but hopefully that's everything sorted now.

[Cuprabob]

Glad you got it resolved.

Is it possible the car was mapped by a previous owner? I have heard of REVO maps causing similar issues in the past.

[Kyleo95]

I think it's unlikely it was mapped before. It only had one previous owner who took it to VW for all servicing and I've had two MOTs since I got the car with no issues.
I've personally stayed far away from any remapping in case of an issue like this!

[Cuprabob]

Certainly something odd has happened then.