Cupra loosing boost pressure randomly

[Cupra_Chris]

Hi Gang,

My cupra made a loud whoosh noise the other day while on full boost and lost power immediately. To me it sounded like a split hose and boost leak, exactly that had happened and I replaced 2 split hoses.

2 days later I'm doing a longer journey and sitting 25% throttle in 3rd at around 5-8 psi and the boost just suddenly drops off but the engine is still revving as it was. It does this every so often while trying to hold the same pressure.

However I thought I would trial and error it and see if it would hit peak boost (if it didn't it would definitely be a boost leak) but it held peak well and didn't drop off at all!?

I removed my aftermarket diverter valve and boost gauge incase there were any splits I had missed but even with factory set up its still dropping off.

I've pulled the wheel arch liner out and had a nose around the charge piping but can't see any loose hoses or anything?

Any help or ideas would be great!

 

[Cupra_Chris]

Just to add I've noticed today it only seems to lose the boost on a certain throttle position in any gear. It did also have surge on full boost in 6th it was jumping between 15-25 psi

 

[R3k1355]

Have you scanned it with VCDS?

 

[Cupra_Chris]

Yep flags up no errors, this is what makes it difficult as it sounds electrical but the ecu can't see an error

 

[Hawkers]

See if a garage can do a smoke test for you.

 

[Cupra_Chris]

I've got it booked in with my local but that's not until next Thursday (bloody covid) it's not chucking out smoke or anything

 

[Hawkers]

Hopefully they can pressure test the air intake and the boost pipes, if any leaks then smoke they pump round will show where the leak is.

 

[Cupra_Chris]

Yea I had seen you can buy them on amazon etc but I doubt I'd use it more than once. I'm hoping it's something simple (and cheap) like that ?

 

[Legojon]

Just to add I've noticed today it only seems to lose the boost on a certain throttle position in any gear. It did also have surge on full boost in 6th it was jumping between 15-25 psi

Tricky one. When you said the revs were hanging, I was thinking pcv. But if it's the same point in every gear, maybe worth cleaning and re-calibrating the throttle body?

 

[Cupra_Chris]

I checked the pcv the other day and it was absolutely fine and clear (I bought the latest revision one prior to going 2+)

Using my multi gauge I switched it to TPS and it usually occurs at around 15% throttle

Throttle body is a pain to get to though isn't it? (intake off etc)