T5 AXB Stuttering After Head Replacement

Evening!

I need your help again.
T5 AXB, 2005, 285,000 km.

Due to a problem where the system would only start after 10 seconds, I replaced the ZK (control unit) including the wiring harness, the hydro unit, and the valves. I also proactively replaced the PDE cable harness. All parts were still original from the factory.

Here's the link to my "starting topic" thread.
/viewtopic.php?t=27871
(As soon as I'm sure, I will post the solution there.)

The PDEs were deeply ingrained in my mind. Of course, I re-sealed the PDEs and adjusted them according to the instructions.
I also need to replace the tandem pump, as it only provides 5-6 bar of pressure.
Der Bully lief aber sonst ohne Murren; seit 10tkm erhöhter Kraftstoffverbrauch; Gefühlt geht ihm im 5. Gang ab 140kmh/3000U/min die Puste aus. KA jolt.

Problem new:
Jerky movement under full and partial load.
Could someone please take a look at the logs?
The quantity deviation was previously normal for all 4, but now cylinder 1 is showing a deviation. Could dirt or debris have gotten in???
The solenoid valve status is abnormal. The wiring harness is new and original VW. Should I reinstall the old one?
Not visible in the log:
With every brief acceleration from a standstill, as the engine speed drops, all 4 valves briefly go to status 4, then to 128, followed by a brief hesitation when reaching the low-speed (LL) RPM, and then back to status 0.
Switching time deviation exceeds -100 (bananas or what?), indicating a fuel shortage. This would be consistent with a tandem pump.

In my opinion, the other measured values seem to be correct.
LMM, boost pressure, ...
I've also attached it just to be sure.

I have sealed the AGR area as part of the work.
It shouldn't matter with the EU3 engine, though.

What is the most systematic way to approach this situation?
Should I swap PDE cylinder 1 with cylinder 2?

I'm not really seeing the connection...

Regards,
Nick.

Quote:

What is the best systematic approach to take in this situation? Should I swap PDE cylinder 1 with cylinder 2?

Here's how I would proceed.

I'd start by taking care of the tandem pump!
Previously, I wouldn't have paid any attention to the values of the LLRR. How can the values be good if there's already too little diesel?

Thank you for your help.

I ordered a new tandem pump.

However, I have little hope that this is the cause.
It was in there before, too.

If that doesn't change anything, I'll reinstall the old wiring harness.
The next step would be to swap PDE Cylinders 1 and 2.
If I didn't have to buy new screws every time, I would do that first...
Then I might as well take them all apart and clean everything.

Where do the failures in the Body Mass Index (BMI) detection originate?
I thought that was always the wiring harness.
Can it be caused by a lack of fuel?

I recall one more point that needs clarification:
The mixing tube! I installed a new one in the new head. However, I couldn't find any indication of its correct orientation, so I installed it in the same position as it was in the old head (with the mark pointing to 10 o'clock or 4 o'clock, when the head is lying on its side ).
Does that sound right so far?

Regards,
Nick.

Quote:

Where do the failures in the GDP detection system come from?

Why should the engine inject fuel during downshifting? Without injection, there's no combustion. That's normal.

Why is the most obvious thing sometimes so far away?

Thank you very much, Rainer.

I'm waiting, but first, I need to get the pump.

Regards,
Nick.

Hello, it's me again...

The Bully is running smoothly again.

Here's what else I did.

Twin-screw pump replaced.
Removed all PDEs, everything has been thoroughly cleaned, and readjusted.
PDE cylinder 1 swapped with cylinder 3.

What exactly was the cause? No idea.
But now it's okay.
Unfortunately, the top speed is still a bit low, at 160 km/h according to the speedometer, but it's approximately the value stated in the registration documents (159 km/h).

And: So far, it always starts up immediately!
At least it's a success, considering the ridiculous 1600 EUR spent on materials, and that's with all the parts looking great for 285,000 km, except for the holes for the pressure drop elements (PDEs). You couldn't have fit an O-ring in those holes, they were that rough (I even cut my finger on the burrs). The rest was good, the hydraulic lifters were actually still okay, but I didn't want to put it back into a brand new cylinder head.

Thank you all very much. As always, super helpful .

I still have one more question regarding the understanding of this.
PDE in Cylinder 1 was up to -1.5 mg/H in the last logging period.
Now, in cylinder 3, the value is ,5.
Can someone explain this?

Regards,
Nick.