this post was submitted on 24 Jun 2025
252 points (97.7% liked)
hmmm
6244 readers
1 users here now
For things that are "hmmm".
Rule 1: All post titles except for meta posts should be just plain "hmmm" and nothing else, no emotes, no capitalisation, no extending it to "hmmmm" etc.
founded 2 years ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
I bet they have VAG COM
I use OBD Eleven
Does that give really detailed diagnostics? I’ve got a GTI that’s showing a P0299 underboost code that’s still around after swapping the turbo and I double checked everything and have no idea what to try next.
I’m not a GTI expert, but have you looked at the diverter valve? Or the charge pipes and connections? Either could be leaking boost, and I had a similar issue with my Mini years ago that turned out to be the diverter valve.
Good luck!
I replaced the diverter valve, same problem.
The charge pipe was disconnected at first after I replace the turbo - metal clip wasn’t locked - but still low boost after that was fixed.
Had my usual mechanic do a smoke test and no leaks.
And the turbo had a brand new boost control valve and diverter valve.
And the other weird thing is my old turbo seemed to be fine, with no play in the wastegate or friction.
lol is the boost pressure sensor bad?
It’s gotta be that or rings because it’s going somewhere. And it sounds like it’s all coming out of your wallet right now. 😅
She’s my first project car and I guess she wanted to be a doozy.
Also if my rings were leaking 8-10 psi of boost you’d think it wouldn’t drive at all, let alone be about as good as a regular Golf
Maybe it needs a good nut blasting in the intakes
ETA: Also my coil packs gave out a while back and my mechanic did a compression test on it and everything was fine.