1.6FSI BAD, inner manifold flaps stuck

[Anelkka]

Hello everyone!

 

I bought second A2 for me as a project. It is with FSI engine and it had some coolant leaks and manifold flaps were cooked from carbon debris.

 

Coolant leaks are now sorted and manifold flaps cleaned. Problem with manifold flaps are still on going. When I did clean the flaps, they were moving nicely and free. After putting everything back together, starting car and successfully done adaptation via VCDS from group 142 everything seems to OK but not really. Couple throttle revs and I found out that flaps are stuck again. I did undo vacuum hose from actuator and actuator arm is completely stuck. 

 

Any ideas what could be the reason before I will dismantle again?

[Lupo_3L]

I'm afraid I cannot ontricute to resolve the stuck flaps, but I can warmly recommend the software from Pro Boost which deactivates the pflaps, resolves also other FSI relate issues and improves driveability signifficantly. It will also deactivate EGR which keeps the injector nozzles clean.

https://proboost.shop/produkte/software-update-audi-a2-1-6fsi/

[Anelkka]

Thanks for reply. I prefer to keep everything original so far. I will dismantle everything with thought maybe in couple weeks and I will update situation after that.

[Krebserl]

I had this same problem a couple of weeks ago with my FSi. The flaps were stuck after a few hours of run time. The problem made me crazy because I dismantled the flaps 3 times until I realized the root cause. The horizontal clearance of the shaft where the flaps are bolted on was obviously too much. When the engine reached its operating temperature the flaps got stuck. After cooling down they didn’t move either so I removed the manifold, checked everything to be moving easily … until they got stuck again. After the 2nd dismanteling I investigated further and could reproduce the problem by hand. When pressing the shaft where the flaps are bolted onto to either side they got stuck. I could see marks from the flaps on the inner wall of the manifold.

So finally I replaced the whole lower manifold.

Rework may be possible by unbolting the flaps from the shaft and removing appprox. 0.5mm on each side of each flap to give it more clearance to the manifold wall. Reducing clearance of the shaft maybe possible with some shims…?
I didn’t take the effort to try it… but I’m sure it can be fixed to save the cost for a spare part.

 

[LiebesKugel69]

vor 17 Stunden schrieb Lupo_3L:

I'm afraid I cannot ontricute to resolve the stuck flaps, but I can warmly recommend the software from Pro Boost which deactivates the pflaps, resolves also other FSI relate issues and improves driveability signifficantly. It will also deactivate EGR which keeps the injector nozzles clean.

https://proboost.shop/produkte/software-update-audi-a2-1-6fsi/

Kann man eigentlich mit der ProBoost Software dann auch die "Drallklappen" komplett im ganzen ausbauen? Diese sind mechanisch Defekt bei mir und Ersatz gibt es ja leider nicht mehr... 

 

Moderator:

***Translation***

 

Can you use the ProBoost software to completely remove the “Drallklappen”? Mine are mechanically defective and unfortunately there are no replacements available...

[Lupo_3L]

vor 2 Stunden schrieb LiebesKugel69:

Kann man eigentlich mit der ProBoost Software dann auch die "Drallklappen" komplett im ganzen ausbauen? Diese sind mechanisch Defekt bei mir und Ersatz gibt es ja leider nicht mehr... 

puh, das kann ich nicht beurteilen, denke aber schon. 
Ursprünglich funktioniert der FSI als Schichtlader wo der Kraftstoff in ein Orbital des Kolbens um die Zündkerze eingespritzt wird. Dieser Schichtladebetrieb wird mit Pro Boost ja eigentlich deaktiviert, also sollten die Klappen keine Funktion mehr haben. 
 

Grok meint:

 

Das ist eine gängige Modifikation bei FSI-Motoren (z. B. 1.6 FSI in Golf, Passat oder Audi A3), um Bruchrisiken zu eliminieren, den Ansaugtrakt zu reinigen und den Luftdurchfluss zu optimieren. Die Software-Deaktivierung (wie ProBoost oder VCDS-Codierung) schaltet die elektronische/magnetische Steuerung der Klappen ab, sodass sie nicht mehr aktiviert werden – aber sie sitzen physisch noch im Saugrohr und können festsetzen oder brechen. Das Ausbauen ist danach unkompliziert und sogar empfehlenswert, da es den Trakt freimacht.

Warum ausbauen, auch nach Deaktivierung?

• Vorteile: Besserer Volumenstrom (bis zu 5–10 % mehr Leistung bei höheren Drehzahlen), keine Verkokung mehr, leichteres Reinigen. Viele Tuner berichten von spürbarer Agilität.
• Nachteile: Leichter Leistungsabfall bei sehr niedrigen Drehzahlen (unter 2.000 U/min), aber das wird durch die Software-Optimierung (z. B. angepasste Zündkarten bei ProBoost) ausgeglichen. Im Alltag merkst du das kaum.
• Rechtlich/TÜV: In Deutschland ist das erlaubt, solange die Abgaswerte passen (kein Leistungsplus über 30 %). Lass es vom TÜV abstempeln, wenn du unsicher bist – oft als "Optimierung" akzeptiert.

Ich persönlich habe nach Proboost Optimierung einen deutlichen Drehmoment Zuwachs im unteren Bereich gespürt. 
Fährt sich wie ein anderer Motor. 

 

 

 

Moderator:

***Translation***

 

Phew, I can't say for sure, but I think so. 
Originally, the FSI works as a stratified charge engine where the fuel is injected into an orbital path of the piston around the spark plug. This stratified charge operation is actually deactivated with Pro Boost, so the flaps should no longer have any function. 
 

Grok says:

 

This is a common modification in FSI engines (e.g., 1.6 FSI in Golf, Passat, or Audi A3) to eliminate the risk of breakage, clean the intake tract, and optimize air flow. Software deactivation (such as ProBoost or VCDS coding) switches off the electronic/magnetic control of the flaps so that they are no longer activated – but they are still physically located in the intake manifold and can jam or break. Removal is then straightforward and even recommended, as it clears the tract.
Why remove them, even after deactivation?

 

    Advantages: Better volume flow (up to 5–10% more power at higher speeds), no more coking, easier cleaning. Many tuners report noticeable agility.
    Disadvantages: Slight drop in performance at very low speeds (below 2,000 rpm), but this is compensated for by software optimization (e.g., customized ignition maps with ProBoost). You will hardly notice this in everyday use.
    Legal/TÜV: In Germany, this is permitted as long as the exhaust emissions are within the limits (no power increase of more than 30%). Have it stamped by the TÜV if you are unsure – it is often accepted as “optimization.”

Personally, I noticed a significant increase in torque in the lower range after Proboost optimization. 
It drives like a different engine. 

 

[Anelkka]

vor 37 Minuten schrieb Krebserl:

I had this same problem a couple of weeks ago with my FSi. The flaps were stuck after a few hours of run time. The problem made me crazy because I dismantled the flaps 3 times until I realized the root cause. The horizontal clearance of the shaft where the flaps are bolted on was obviously too much. When the engine reached its operating temperature the flaps got stuck. After cooling down they didn't move either so I removed the manifold, checked everything to be moved easily … until they got stuck again. After the 2nd dismantling I further investigated and could reproduce the problem by hand. When pressing the shaft where the flaps are bolted onto either side they got stuck. I could see marks from the flaps on the inner wall of the manifold.

So finally I replaced the whole lower manifold.

Rework may be possible by unbolting the flaps from the shaft and removing approx. 0.5mm on each side of each flap to give it more clearance to the manifold wall. Reducing clearance of the shaft maybe possible with some shims…?
I didn't take the effort to try it… but I'm sure it can be fixed to save the cost for a spare part.

 

Actually I discovered this same thing when manifold was at table. Good idea about grinding flaps little bit, I will sort out this one. Thank you for replying

[Nagah]

Moderator:

@LiebesKugel69 @Lupo_3L

Can you please stick to English in the "English language forum"?

If you are not able to read/write English, you can just use a translation tool of your choice.

 

But writing German in the English forums is rude.

 

Thanks mates!

 

- Nagah

[PlasticMac]

On 11/23/2025 at 1:18 PM, Anelkka said:

Actually I discovered this same thing when manifold was at table. Good idea about grinding flaps little bit, I will sort out this one. Thank you for replying

Hi,

Interesting finding. Which side of the flaps is touching the manifold wall? The side farthest from the actuator end, or nearest?

Mac.

[Krebserl]

I had touch marks on all four walls related to all 4 flaps. The marks were always on the right side of the walls looking from the front onto the flaps. I dismanteled a lower manifold and the shaft where the flaps are bolted onto has clearance, so all flaps are covered. The tolerances are quite small so I would rework all flaps on each side. We don’t know which direction the shaft is moving under operation, could also move to the other direction. So when doing the rework do it only once and right…. Remove material on both sides. Alternatively make the clip in the middle of the manifold a little bigger (new from 3-D printing) to avoid clearance of the shaft. This plastic clip secures the shaft in position and avoids hoeizontal movement of it. 

[Anelkka]

Inner manifold is now disassembled again. Seems like my repaired actuator's arm got broken again from gluing. I made it a bit too thick and maybe that caused it to broke. I took some video how flaps are moving when using vacuum. Is it normal that values from VCDS are about ≈ 10% when flaps are open and ≈ 90% when closed ? Does it effect when doing adaptation via channel 142?

 

If somebody has unbroken or repaired actuator laying on the shelf, I am interested!

 

I also did tried to remove bolts that are connecting flaps but they seemed to be really tight so I did leave as they are.

[Anelkka]

https://drive.google.com/file/d/1UypBw8MqOJZCxkJzlNpbulJDhN6YaH67/view?usp=sharing

[Krebserl]

First of all once you installed the lower manifold and move the flaps the movement is less than when you do this with the manifold outside (comparing values in VCDS). This means the values do not reach 0% or 100%! 

In the next step after reassembly of the manifold you have to adjust the values of the potentiometer in VCDS doing a basic setting (ignition on, engine on running idle) until “ADP io” shows in field 4 of  MWB 142, only then the values in field 1 move from  0% to 100% and back.

 

[Anelkka]

Thanks for information. I have now repaired actuator's arm again, lets see how it works out. 

 

Okay, so its normal that when manifold is installed values don't reach 100% and 0%. I will link couple images and a video how arm is repaired with M6 bolt and some epoxy.

 

https://drive.google.com/file/d/11rXeL2pODp9RlcB_mlts3OUzTH__s1OA/view?usp=sharing, https://drive.google.com/file/d/13hth3PiKGYKag0QL7G9bh4ca_yxx0WD5/view?usp=sharing, https://drive.google.com/file/d/1BrD1taPWYoLD8WVySsKlFAR7PzFzZkx6/view?usp=sharing, https://drive.google.com/file/d/1BtcMaPD92nkLzov_8ZqbKjtkNO4i8gwO/view?usp=sharing, https://drive.google.com/file/d/1HscT4hautTqQjIEa8CV0OmzHvnc8AZZd/view?usp=sharing, https://drive.google.com/file/d/1_qi3qBpUFYec2xJUdIP6E6asB9kWFRD6/view?usp=sharing, https://drive.google.com/file/d/1q6SeNCZ_Rg8M0O7NFwGcAEJ7wmy-ANyA/view?usp=sharing

[Krebserl]

Interesting repair method for the actuator arm.
 

I habe inserted a steel rod with 2mm diameter after drilling a corresponding hole and plastic welded the part in addition. Works fine since the repair. If I ever need to fix another actuator, I will add a thread at the end for the actuator to manifold connection. Then turn a fitting piece with thread on a lathe to connect to it and the manifold so I can remove the actuator without disassembling half the motor… 

[Anelkka]

Your repair looks much more cleaner than mine haha. Thanks for pictures!

 

 

[Anelkka]

Saga continues. I did remove some material from manifold for the flaps just a bit to make sure they dont stick. However it didn't help, flaps gets stuck still after starting car. I am now pretty sure that problem is in the head. 

 

If I manage to remove flaps completely, does ECU understand that pontentiometer's shaft is moving over its limits? What I did try out when manifold was out from head and plugged potentiometer connector, is that VCDS showed values from 0% to 100% but at very end of movement values doesn't change. I would guess that it dont make any error codes if shaft moves freely and adaptation is succesfully made.

[Krebserl]

vor 3 Stunden schrieb Anelkka:

Saga continues. I did remove some material from manifold for the flaps just a bit to make sure they dont stick. However it didn't help, flaps gets stuck still after starting car.

So when you have removed some material and the flaps move easily without stick slip effect with the manifold being outside the engine, are you sure you did assemble the manifold correctly ? Means you fixed the flaps with a 3mm drill in open position.

Also if the manifold is not seated perfectly (because the rubber seals of the injectors are sticky and can’t be inserted completely in the brass fittings) it can cause the flaps to stick. I lubricate the o-rings of the injectors before assembly. The brass connectors o-rings are also lubricated and are completely seated in the manifold before assembly.
Before tightening the screws you have to check and move the flaps to verify they still move. If you tigthen the screws too much, this can cause the flaps to stick as well.

Is the vacuum actuator working correctly?  I had a problem with the seal of my vaccuum, there was a tiny hole in the rubber. So the force of  the vacuum actuator unit was too low. I replaced the rubber with a new one from a similar unit. The diameter of VAG units is same on most engines.

 

[Anelkka]

Thank you for replying. 

 

Yes I did use some drill to hold flaps into its frame. Also I did verify when manifold is tightenet that actuator arm is moving still.

 

Every time when I have refitted everything and start car, I manage to make adaptation succesfully once. After couple throttle chirps I can see from VCDS that ADP. OK changes to ERROR and actuator arm is stuck.

 

The actuator itself holds vacuum, so I dont think its the problem.

 

If the sealing from injectors is not correct I would assume that it leaks fuel as well?

[Krebserl]

vor 27 Minuten schrieb Anelkka:

If the sealing from injectors is not correct I would assume that it leaks fuel as well?

No the rubber O-rings will seal, but the manifold is not fully seated, this can be only 0.5mm. Then the manifold gasket is not fully sealing and the flaps can stick.

I had this problem when I did the reassembly the first time. Meanwhile I have replaced quite some injectors on BAD, so I know the possible mishaps.

 

Anyway, have you checked the axial clearance of the shaft holding the flaps. When you have disassembled the manifold and move the flaps with a vacuum pump and push the shaft firmly to one side (from actuator side). What happens? Do the flaps touch one side of the manifold and get stuck? 

If so, then you have this effect also after assembly. If there is sufficient clearance between the flaps and walls of manifold and you can't get them stuck, then the problem is either the vacuum actuator or a problem during assembly.

in first case you need to remove more material from the flaps or try to reduce the clearance of the shaft. In the center of the manifold there is a black plastic part inserted. This is a clamp that fits into a notch of the manifold shaft and limits the axial movement. if this part is worn, the shaft can move axially

and thus make the flaps touch the walls to get stuck. Replacing this part e.g. with a wider part printed in 3D can cure this problem.

[Anelkka]

Interesting. Maybe next time when assembling inner manifold I will check with feeler gauge is it fully seated.

 

I did check axial clearance when manifold was out. I noticed that if shaft (actuator side) is pushed little bit, flaps will stick to other side. Thats why I did remove some aluminium from manifold itself. Now there should be enought clearance.

[Krebserl]

It is easy to dissaemble the manifold shaft and all the flaps. Overall 15min to completely disassemble it. Then you can remove material with a belt sander from the flaps. 
I would rather do this than grind / sand on the walls of the manifold.
It is difficult to reach all areas with the flaps still in place and even more difficult to be precise….

Since sticking flaps are an annoying error and disassembly of the manifold is also a pain in the ass I would make a solid overhaul once, then you have peace of mind for the next 100k mls. But it is your choice what you do.

[Anelkka]

Thank you for pictures!

 

Yesterday I did disassembly flaps away completely. Now car is running without flaps and no error codes. However after longer testdrive, I am pretty sure that headgasket is gone. When car is running, pressure build up to resevoir and coolant starts to leak from hose connectors. I bought car as a project and there was first issue with cooling system. Waterpump's plastic impeller was cracked and it was overheating. I replaced waterpump, "death pipe", thermostat but now its time to get head out as well

 

 

Is there any disadvantages to run car without flaps? At least now its running without any error codes.

Bearbeitet 20. Dezember 2025 von Anelkka