Leon Cupra ST 2019 300 high rpm, high consumption

[vozlov]

Greetings,

so, to start, we bought the car 2 years ago, didnt like the sound, emptied the mufflers. Wasn't enough, we took out GPF/OPF and mapped it. All was well, till about half a year back, when she started drinkin gas like there's no tomorrow, goin from 21mpg to 15mpg over night. We changed the PCV valve with a knock off and it worked till a week back, when she started doin it again. Now, wwe changed it with an OE but things are not well. She's got high idle (like she's always in coldstart), does about 14mpg.
We took it to a local shop, checked and there's no active GPF regeneration (had to check, even if she's got no GPF), no fault codes, no nothing.

My question, what could possibly be wrong, before we take her to 4 more shops and no results...

Thank you so much in advance.

 

[nd-photo.nl]

-Check the fuel trims, this will probably point you in the right direction
-Might be lamda related

Did you add / change other hardware? Like a blowoff plate (or blowoff valve)?

 

[vozlov]

Hey, thank you, will mention it and check. Lamda should put out a code, no?

No, nothing else was added, other than 63 ornamental cats all over dash and rearview mirror..

 

[nd-photo.nl]

Using VCDS, you can check measuring blocks to see if the lambda is doing something.

https://www.ross-tech.com/vag-com/m_blocks/030-049.html

Someone mentioned here not to long ago a weird situation where the 2nd lambda sensor was requesting 100% fuelling all the time, could also be the case who knows.

Might be handy to know your mileage?

 

[vozlov]

Awesome answer, thank you so much.
She's at about 80k miles.

 

[mty12345]

Greetings,

so, to start, we bought the car 2 years ago, didnt like the sound, emptied the mufflers. Wasn't enough, we took out GPF/OPF and mapped it. All was well, till about half a year back, when she started drinkin gas like there's no tomorrow, goin from 21mpg to 15mpg over night. We changed the PCV valve with a knock off and it worked till a week back, when she started doin it again. Now, wwe changed it with an OE but things are not well. She's got high idle (like she's always in coldstart), does about 14mpg.
We took it to a local shop, checked and there's no active GPF regeneration (had to check, even if she's got no GPF), no fault codes, no nothing.

My question, what could possibly be wrong, before we take her to 4 more shops and no results...

Thank you so much in advance.

First thing i would look for is an intake leak. That can cause high idle and wouldn't throw a code. If you have a smoke tester then i would smoke test, if not then just visual inspection

 

[vozlov]

First thing i would look for is an intake leak. That can cause high idle and wouldn't throw a code. If you have a smoke tester then i would smoke test, if not then just visual inspection

Looking at intake manifold mostly, or where?

Thank you!

 

[mty12345]

Looking at intake manifold mostly, or where?

Thank you!

Check all the PCV pipes and also all the intake pipes that are after the MAF, so intake manifold, intercooler piping etc etc. Smoke testing makes it much easier, but if not then get a flashlight and have a good check of all the pipes.

 

[nd-photo.nl]

You can also try the "brake cleaner" method, spraying brake cleaner while the car is idling and see if the rpm changes.

 

[SuperV8]

Using VCDS, you can check measuring blocks to see if the lambda is doing something.

https://www.ross-tech.com/vag-com/m_blocks/030-049.html

Someone mentioned here not to long ago a weird situation where the 2nd lambda sensor was requesting 100% fuelling all the time, could also be the case who knows.

Might be handy to know your mileage?

I would also look/log your temp sensors to make sure they are doing something meaningful.

Agree on Lambda sensors, they only have a finite life typically 60-100k miles - and can be damaged by contamination/thermal shock/Rich running.

 

[nd-photo.nl]

@SuperV8 Correct, if your engine is not up to temp, it will keep running rich if I remember correctly. A faulty temp sensor can do that for you

 

[vozlov]

Hey guys, a little update. I called around and got me a specialist who can take a look with vcds next week, but I've managed to get a reading of lambdas at MOT and they are fine (MOT wise, could still be defect). We pressure tested intake and no leaks, no new codes, so till next week, I know nothing.
Thank you again for your opinions and instructions!