Stalling at high speeds up hill

[JulesArch]

Hi,

We are desperately trying to understand and fix a long term problem we've had with our 2005 Passat TDI wagon. There's so many nice things to say about this car, however we are on the verge of donating the car instead of an endless issue that has so far defied root cause and a fix.

Here's the description: when going up lengthy hills at high speed, the engine starts to sputter a bit, losing speed and power. It gradually gets worse, and pushing the accelerator to the floor does not make the car go any faster. The last time this happened, the car literally stalled, and we had to pull over on the highway---very scary event! When trying to re-start, the engine turned over but did not start. Finally, after a few minutes, the engine did re-start, and our drive resumed without incident.

We have tried in the past to have dealer service look into this, but without any fault codes, they don't really know where to begin...Has anyone had this issue, and if so, what did you do??? we've tried simple things so far like fuel filter replacement, but nothing seems to make a difference...


Thanks!

 

[CantWrite]

So this long term problem, does it happen on every long pull at high speed?

After this last time, and it restarted, did it sputter and stumble like there’s air in the system?

Does it start fine after sitting all night or does it sputter?

My uneducated guess is air intrusion or tandem pump not able to meet fueling demands.

How many miles on car? How long have you owned it? Any mods?

Good Luck, and there are some very smart folks on here!!

 

[JulesArch]

Thanks for the quick reply!

Our 2005 Passat TDI wagon 'only' has ~140K miles on it. Nonetheless, the car has had this problem ever since we bought it (used) eight years ago when it had ~100K miles. We have not done any major 'mods', but have had several issues that were fixed over the years, including:
a new turbo (2017,2020), and new engine control module (2017), glow plug harness (2x).

The car has no issues at all starting after sitting all night.
The last time it happened, it seemed to sputter and shudder like it doesn't have sufficient fuel, not as if there's air in the system.
It seems to happen ONLY when going up-hill for a significant interval, but happens almost all of the time to a greater or lesser degree.

Hope this description might help those experts out there!

Thanks!!

 

[CantWrite]

sidebar: Oil hammer has mentioned these turbos are pretty durable, why has yours needed 2?

do you baby the engine? Could the “Shudder” be a hot transmission Torque Converter issue?

have you tried a different Tandem Pump? Is your Lift Pump working?

Story time: I have a ‘92 E350 7.3 IDI NA diesel. I live at 7500’ and routinely go over 10k’. I know what it’s like to be in a gutless diesel going uphill. It doesn’t sputter or shudder though, just slows, and pushing t he pedal just spews smoke.

So I would think temp related or fuel flow. Do you have VCDS? Have you check for stored codes in your TCM?

 

[zzdiesel]

I had one acting like that. My 1st guess would be the tandem pump. About a 200 dollar item if you get a Pierberg, plus instalation. If it was making black smoke when the incident occured I might guess camshaft.

If there are no codes it rules out a lot of things such as turbo boost problems.

 

[P2B]

My first guess would be a failed lift pump, on the theory the tandem pump is able to supply sufficient fuel without help except during a long uphill run.

 

[Windex]

^this is where I would start.

Any difference if the tank is completely full?

 

[JulesArch]

Thanks to all for their ideas and suggestions! Will focus on the pump theories. Not sure about difference if the tank is full or not.

Quick question: how would one be able to test for a failed lift pump?