Please help, STILL overboost condition when lifting.

[Caymanjp]

Hi Everyone!!

Was hoping someone here could help me as dealership was no help!

I have given my beloved golf (2008 FSI GTI) so much love and care but have this lingering issue I’m really struggling with!

Basically my turbo was replaced last year and it spools great and ran great for many months! The car runs great under normal driving conditions but should I put my foot down 3/4 of the way or more and let go of the gas the car jerks quite hard and I get the CEL with the code P0234 (Turbocharger overboost condition).

Only happens when I suddenly let go of the gas, It’s like it’s unable to dump the boost it’s built up. If I run it really hard into the 5500-6000RPM range it occasionally throws a underboost code. MAP sensor has been replaced and only has a couple miles on it.

Just hoping someone has had a similar experience or knows what the likely culprit is. Thanks in advance!

Mileage is around 88000miles

JP

 

[GIACUser]

Could be that your diverter valve is stuck, which would cause a surge when you let off of throttle and you might hear some new fluttering noises.
You should fix this now to avoid any damage if this is what is going on.

 

[Caymanjp]

Could be that your diverter valve is stuck, which would cause a surge when you let off of throttle and you might hear some new fluttering noises.
You should fix this now to avoid any damage if this is what is going on.

Thanks, that is what I was thinking could be the problem because I have occasional flutter as well. Vehicle is my daily driver so I’m treating her real gentle and keeping RPMs low. Will get one ordered and hopefully that’ll fix it. Thanks for your input!

 

[GIACUser]

Post results, let us know how it works out.

 

[Keehs360]

This is happening because your turbo can’t vent or recirculate. I’m not sure how the mkv’s are set tbh

your dv is either stuck. Or for some reason it lost its reflexes and can’t react in a way that would meet the programming’s standard.

I’d also start at the dv. This behavior can be seen on a log too, do you have one? If so I don’t mind checking it out.

 

[Caymanjp]

This is happening because your turbo can’t vent or recirculate. I’m not sure how the mkv’s are set tbh

your dv is either stuck. Or for some reason it lost its reflexes and can’t react in a way that would meet the programming’s standard.

I’d also start at the dv. This behavior can be seen on a log too, do you have one? If so I don’t mind checking it out.

Thanks! New revision piston DV has been ordered. Unfortunately I have a pretty generic and basic scan tool so I am only able to log basic blocks such as fuel rail pressure, air flow and temperature etc. I definitely need to look at getting a more VAG orientated scanner.

Thanks! Will update when the part is in

 

[Chumeta]

Dv

 

[Caymanjp]

If the diverter valve is faulty doesn’t the turbo usually just underboost? I know the older variations have tearing issues where boost leaks. But this wouldn’t cause an overboost?

 

[GIACUser]

If the diverter valve is faulty doesn’t the turbo usually just underboost? I know the older variations have tearing issues wher

My guess his is either disconnected or he has a piston type and piston is frozen. What he describes indicates it is not opening up and releasing pressure when he lets off accelerator
In this case he is letting off throttle, closing throttle flap and trapping pressurized air between throttle plate and turbo. Normally diverter valve opens at this time. His is not, so that pressurized air is trying to go out through turbo creating the fluttering noise as the pressurized air is pushing back into the turbo blades.

 

[Caymanjp]

My guess his is either disconnected or he has a piston type and piston is frozen. What he describes indicates it is not opening up and releasing pressure when he lets off accelerator
In this case he is letting off throttle, closing throttle flap and trapping pressurized air between throttle plate and turbo. Normally diverter valve opens at this time. His is not, so that pressurized air is trying to go out through turbo creating the fluttering noise as the pressurized air is pushing back into the turbo blades.

Afternoon all, thanks to everyone for your replies. Today my new OEM DV arrived and I rushed to get it installed! I was extremely excited to get it in, the installed DV was a random piston type without any markings or branding so I'm glad I got it changed out. Wiring seems to be in perfectly good condition and I cleaned out the connector before installing the new one. After installing I cleared the codes and took her for a drive, I was unable to get the flutter I got before which is great but alas occasionally when I get off the gas between 3-4k RPM I still get the hard shudder followed by the overboost code.

I cleared the codes again and also tried applying 1/2 throttle to try get through the rev range, around the 3-3.5K RPM range the car stops boosting and drops into limp mode with the same P0234 overboost code. I don't know what else to look at, I have the actuator which I believe is called the N75 valve also ordered and is on the way but except for that I have no idea what else to try. Any suggestions would be greatly appreciated, trying to avoid heading to the dealer but it's starting to look inevitable.

Thanks again everyone!

Regards
JP

 

[Keehs360]

Thanks! New revision piston DV has been ordered. Unfortunately I have a pretty generic and basic scan tool so I am only able to log basic blocks such as fuel rail pressure, air flow and temperature etc. I definitely need to look at getting a more VAG orientated scanner.

Thanks! Will update when the part is in

 

[Keehs360]

Afternoon all, thanks to everyone for your replies. Today my new OEM DV arrived and I rushed to get it installed! I was extremely excited to get it in, the installed DV was a random piston type without any markings or branding so I'm glad I got it changed out. Wiring seems to be in perfectly good condition and I cleaned out the connector before installing the new one. After installing I cleared the codes and took her for a drive, I was unable to get the flutter I got before which is great but alas occasionally when I get off the gas between 3-4k RPM I still get the hard shudder followed by the overboost code.

I cleared the codes again and also tried applying 1/2 throttle to try get through the rev range, around the 3-3.5K RPM range the car stops boosting and drops into limp mode with the same P0234 overboost code. I don't know what else to look at, I have the actuator which I believe is called the N75 valve also ordered and is on the way but except for that I have no idea what else to try. Any suggestions would be greatly appreciated, trying to avoid heading to the dealer but it's starting to look inevitable.

Thanks again everyone!

Regards
JP

Shit. At this point I’d take it in bro.

edit. Spelling. Sorry. Take it into a shop is what I meant.

 

[GIACUser]

Afternoon all, thanks to everyone for your replies. Today my new OEM DV arrived and I rushed to get it installed! I was extremely excited to get it in, the installed DV was a random piston type without any markings or branding so I'm glad I got it changed out. Wiring seems to be in perfectly good condition and I cleaned out the connector before installing the new one. After installing I cleared the codes and took her for a drive, I was unable to get the flutter I got before which is great but alas occasionally when I get off the gas between 3-4k RPM I still get the hard shudder followed by the overboost code.

I cleared the codes again and also tried applying 1/2 throttle to try get through the rev range, around the 3-3.5K RPM range the car stops boosting and drops into limp mode with the same P0234 overboost code. I don't know what else to look at, I have the actuator which I believe is called the N75 valve also ordered and is on the way but except for that I have no idea what else to try. Any suggestions would be greatly appreciated, trying to avoid heading to the dealer but it's starting to look inevitable.

Thanks again everyone!

Regards
JP

"I cleared the codes again and also tried applying 1/2 throttle to try get through the rev range, around the 3-3.5K RPM range the car stops boosting and drops into limp mode with the same P0234 overboost code"

Is this symptom new? So while accelerating the car falls on its face and goes into limp mode? Also, is there any work under the hood that occurred just before this or your original problem arose?

 

[Caymanjp]

"I cleared the codes again and also tried applying 1/2 throttle to try get through the rev range, around the 3-3.5K RPM range the car stops boosting and drops into limp mode with the same P0234 overboost code"

Is this symptom new? So while accelerating the car falls on its face and goes into limp mode? Also, is there any work under the hood that occurred just before this or your original problem arose?

That specific symptom is new after the fresh DV install. It feels like someone basically switches off the turbo while I’m accelerating. No work was done, it just started happening one day. Both the new map sensor and DV seem to make an improvement but the underlying issue is still there.

 

[Keehs360]

That specific symptom is new after the fresh DV install. It feels like someone basically switches off the turbo while I’m accelerating. No work was done, it just started happening one day. Both the new map sensor and DV seem to make an improvement but the underlying issue is still there.

Could it just be the relearning process?