1.2TDI gets harsh clutch behaviour over time and then wont start

[Joakim]

Hi

As my German skills are somewhat limited (= what I learned in Swedish school as my third language over three-four years, like 35 years ago) I will write this post in English to save you the frustration of reading my bad German texts 😉.

One of my A2 1.2TDI (2001) is not always reliable over time.

I first noted this last summer when it wouldnt start after a short restaurant visit. I checked that the brake light switch and light was ok, but only after zapping slightly on the cluch wire I managed to get it to start.

I could notice uncomfortable cluch control while driving back.

After that I checked some clutch values with VCDS followed by a GGE which solved the issue. The car then started and drove well again, as it usually had.

 

But now after taking the car back in traffic after having spent winter standing still in a garage, and driving it some weeks problems started again.

I noticed rough clutch engagements after stopping at crossroads, and bad gear changes. I quickly disengaged ECO to avoid engine shutoffs at crossroads and headed home.

After turning it off it couldnt start again (as I feared/ suspected).

Please see my screenshot from VCDS at this point.

What conclusion can be made, if any?

I noticee the 12.5% value. 

Is this the reason for not enabling the starter?

I.e has something caused the GECU SW adaptive algoritms to malfunction or what?

Bearbeitet 11. Mai 2025 von Joakim

[Mankmil]

Hello Joakim, how many kilometers has the car run? Is it around 250.000 km with the fist guide sleeve? This is a very common issue at this mileage.

After exchanging it, you're ready for the next 250.000km. When I remember correctly, you've a modified clutch actuator installed?

[Joakim]

Hello Michael.

It has now done approx 364 000 km since it left the factory.

At 297 350 km ( in 2015, before my ownership) the clutch cylinder, the guide sleeve, the fork, clutch kit and even the brake switch was renewed at a reputable one-man 3L specialist workshop.

I bought it in 2020 at around 340 000 km and it worked well until last summer (2024) at around 360 000km.

So to conclude, less than 70 000km since new clutch kit and cylinder. To my knowledge the clutch cylinder was a genuine Audi one, not a Hall modified, but not 100% sure since the bill only states clutch cylinder to a cost which corresponds to around 330 Euro.

 

 

Bearbeitet 11. Mai 2025 von Joakim

[Lupo_3L]

Hi Joakim,

 

I don't have the solution but it hppened to me twice after two long 400km and 500km rides. I already have a factowy new clutch cylinder and also my clutch is almost new, so I would say these components are not the issue.

Once I drove 400km from Vienna to Praque with higher speeds and when arriving in the city center, I noticed rough clutch engagement. After stopping it would not start. Luckily I always carry my VCDS with me on long trips so I could start the Basic Settings and everything was fine afterwards.

I also have to say that on the yourney I had very little shifts since I keep the 5th gear engaged on the higway because with 95HP it's basiclly not necessary to leave 5th gear on the highway.
Second time 500km Vienna Garmisch-Partenkirchen. Almost only highway and very few gear changes. After stopping, the car would almost jump due to harsh clutch engagement.
Then basic settings and again everything was fine.

Last time was 50.000km ago and it did not happen again.

The clutch Voltage did not change at any time so I have no plausible explanation for this issue. Maybe driving a few hours withshout any single gear change could be the cause since the GCU might adjust the slipping point while driving.

Bearbeitet 11. Mai 2025 von Lupo_3L

[Joakim]

Aha, interesting that it has happened also to others.

I can add that I have now made an GGE again and the car can now start again and drives normal, just as last time.

But I dont think the actual problem is long term solved.

[Lupo_3L]

Well, it did not happen since 50.000km so I would say  it's done.

[Lupo_3L]

Seems I found the solution.

 

 

The clutch cylinder soaks with oil which lowers the resistance, hence the system adjusts the clutch value downwards.

[leiseflieger]

Hi Joakim,

the 12.5% clutch value when the TCU commands the clutch closed is concerning and it will in fact disable the starter.

The clutch adaptation works like this: The TCU tracks the lowest G162 value ever seen since the last basic setting. For the TCU, this voltage equals to 0% clutch. 100% clutch is defined as the lowest G162 voltage (e.g. 1,9 V) plus a fixed offset of 2,04 V. Meaning that when everything is set up according to factory instructions, the clutch position ranges from 1,9 V (0% normalized) to 3,94 V (100% normalized).

The bite point and creep points are placed somewhere in the upper half of the normalized range. These are adapted constantly during operation.

One of two things happened with your car:
 

• The guide sleeve or some other mechanical part of the clutch failed and your clutch is physically unable to close fully.
• An fault in G162 or its wiring caused the G162 value to read low momentarily. The TCU has adapted the voltage for closed clutch to this value (e.g. 1,1V) and the normalized clutch range has now shifted. Although the clutch is closed, the TCU interprets it as 12.5% open due to the mis-adapted values.

You could be a victim of a low quality aftermarket throwout bearing or guide sleeve which has failed prematurely, or your G162 has worn out or is contaminated with oil. The symptoms you described make be believe the latter is more likely.

A basic setting will provide a short term fix. It is likely that the same thing will happen again, with increasing frequency. For now, take your cable and laptop with you. It could save the day. Long term, use a boroscope to inspect the clutch mechanics and be prepared to invest in a new clutch cylinder.