(desperately) Looking for help/Advice with my T6 TSI stalling in specific situations

[peter1987t]

Dear all,

I am (in desperate) need of help with my TSI, bear with me, it requires a bit of context.

About the car:

• Model: VW Transporter T6 Kombi (2017)
• Engine: 2.0 TSI (CJKB manual gearbox)
• Fuel system: LPG (Prins)
• Mileage: ~111,000 km
• History: Full cylinder head rebuild ~16,000 km ago due to burnt valves. Recently, the garage replaced the throttle body in an attempt to solve the issue. Smoketest has been executed (although I have not seen it myself, and there were apparently no leaks).

The Problem:

1. Running on Petrol,
   When I press the clutch (often 2 times in a row while shifting back to a roundabout), often revs drops under the idle rpm, not directly an inmediate issue, but worthwhile noting and only happened as far as I know after the engine head revision.
   
   
2. Running on LPG + running Airco
   Same thing happens, but often the engine is responding too late and the motor stalls completely, resulting in dangerous situation. (all systems shutdown).

The garage claims the above described behaviour is normal, and advised me to remap the LPG such that it respons properly and doesnt dip as low.
In my opinion - since the car did not show this behaviour before the revision, it is an issue in the engine itself and not in the LPG system. To me, this sounds like putting a bandage on instead of resolving the real issue.

Is there someone who can help me? I am even willing to make the drive to the UK if there is someone who is seriously able to diagnose the problem.
Let me know what other information I need to share.

PS I tried gemini and its constantly hammering on "Missing or Incomplete Throttle Body Adaptation (Most Likely)", my garage was sure it was not needed.

Thank you!

best regards,
Peter

 

[Dellmassive]

Dsg? Manual?

Got access to vcds diagnostic?

 

[SimeonT6]

I'm not clear whether you're saying this behavior is since the head rebuild, but if it is start with the basics .. static timing.

 

[peter1987t]

Dsg? Manual?

Got access to vcds diagnostic?

Its an manual gearbox, i dont have vcds, but I probably can reach out to someone when needed and i know where to look. I would be able to monitor the behavior on Petrol, but the odb connector is unavailable when running on LPG. But the behaviour should still be there.

I'm not clear whether you're saying this behavior is since the head rebuild, but if it is start with the basics .. static timing.

I am 100% sure the behaviour wasnt there before. Can you help me with "static timing?" Is there something i can verify? Or is this something i need to let a mechanic check?

Situation is that the garage who executed the revision (in collab with the revision company) doesnt know what do to do next and discussions and arguments are heated up.

 

[SimeonT6]

I'm not sure on the specifics of your engine, but any garage should be able to check it. Alternatively VCDS might tell you, again not sure on these engines as I've mostly messed with older stuff.

If the garage has run out of ideas it's time to talk to a different garage, if only to check the basics are 100% so you know your base position is correct - timing, fuel, compression, spark. If those are all correct you can start elimination of other things.

In your P.S. comment you state 'your garage was sure it was not needed' .. which is pretty concerning, it takes 5 mins to plug in and click the button for throttle body adaption so they really have no reason not to try it.

 

[peter1987t]

I'm not sure on the specifics of your engine, but any garage should be able to check it. Alternatively VCDS might tell you, again not sure on these engines as I've mostly messed with older stuff.

If the garage has run out of ideas it's time to talk to a different garage, if only to check the basics are 100% so you know you're base position is correct - timing, fuel, compression, spark. If those are all correct you can start elimination of other things.

In your P.S. comment you state 'your garage was sure it was not needed' .. which is pretty concerning, it takes 5 mins to plug in and click the button for throttle body adaption so they really have no reason not to try it.

Context
Its has become quite frustrating and costly and customer/client relationship is heating up from that perspective. They've already made quite some costs but without no real outcome and methods of verifications like smoketest or a throttle body adaption is something I need to mention myself. This is where I would expect some sort of self inititiave from the garage itself. They've replaced my throttlebody, but without any results, and threw away the old one (or atleast, I asked for it but it was gone). On the otherhand, in my opinion its an warranty topic, and I want them to fix it, but I ran into an dead end and not yet willing to start some sort of legal case.

Anyway, I have a carista ODB 2 with an subscription, I think I can do the throttle body adaption myself, I can do this without any hazard I assume?

 

[SimeonT6]

Problem is, if they can't fix it (i.e. incapable, baring in mind fault finding in a modern engine is a pretty specialist job) no amount of legals is going to change that. The best thing to do is get another garage to look at it, sometimes a fresh set of eyes and ideas is enough, then if you know what it is they can fix it under warranty.

No risk with an adaption if Carista can do it.

 

[peter1987t]

Ill see if I can do the adaptation tomorrow, ill come back here.

 

[peter1987t]

Did the throttle body adaptation yesterday, in the end did it twice to be sure.

Unfortunately, no luck.





Hereby the exact behaviour recorded, the language is dutch, but I assume its clear enough:

Some additional info about what has been done on the car lately:

1. February 2025: Mechanical Cylinder Head Rebuild​

Heavy mechanical overhaul to address base engine health.

• Cylinder head: Dismantled, skimmed, and cleaned. Fitted with new intake valves, exhaust valves, and valve guides. Valve seats refaced.
• Engine sealing: New head gasket, head bolts, and exhaust manifold gasket.
• Timing: Complete timing chain replacement, including all tensioners and guide rails. Crankshaft seal renewed

Issues as described started here

2. April 2026: Intake Tract, Cooling & Software​

• Cooling system: Water pump module replaced, including specific water pump gaskets and fresh coolant.
• Intake tract resealed: Intake manifold removed. Intake manifold gaskets, throttle body gasket, and teflon fuel injector seals were fully replaced with brand new parts.
• Diagnostics & Software: A smoke test was performed (no leaks found) but have not witnissed it myself.
  

Exclusions (so far?)​

Based on this chronology, the following variables can be ruled out?

1. Vacuum leak via intake gaskets: Ruled out. The manifold, throttle body, and injector seals are less than three months old. and smoke test has been done.
2. Engine software mismatch: Ruled out. The abrupt drop to 550 RPM was identical on both the old and new software versions.
3. Missing throttle body base setting: Ruled out.

What should I do next?