2.0 JTD with Bosch EDC15: Very low power output below 2500 RPM

Hello everyone, I'm new here. I'm a technically inclined person who likes to do things myself, and I'm having a problem with my Fiat Ulysse 2.0 JTD from 2001.
The car has a 109 horsepower JTD 2.0-liter engine with a Bosch EDC15 PSA engine control unit.
Since there is hardly any power output below 2500 rpm, but the turbocharger starts to become noticeable above that, I had the error memory read out at FIAT with the following result:

1. Check diesel fuel pressure; pressure is below the target pressure.
Sporadically.
Possible causes: Pressure regulator not functioning, Pressure regulator blocked.
Fuel leaks in the high-pressure diesel fuel circuit [there are no leaks, so I can rule that out].
2. Fuel low-pressure pump supply, K.S.: against ground/control unit [????]
Sporadically.
Possible causes: Relay power supply issue, wiring harness fault, faulty relay, defective diesel fuel pump, defective control unit, damaged connectors.

Since the car was already reaching its maximum speed, I would have suspected a mass airflow sensor issue.
It starts well, runs smoothly, but it doesn't have much torque below 2500 RPM.

I've noticed that once the engine has built up pressure (i.e., above 2500 RPM), and I shift quickly, there's still power available just below 2000 RPM. Then it drives normally and quickly. However, if I continue driving at 2000 RPM and then accelerate again later, the power is lost again.
To me, it looks more like a lack of boost pressure.
Oh yeah, and when it's cold, it has more power at speeds below 2000 RPM.
Could someone please give me some advice on this error message?

I have an appointment with Bosch next week, but I would like to learn more about it beforehand.


Thank you & Best regards.
Ralf.

Hello again,

Is there anyone here who can say something about this?

Best regards.
Ralf.

marlasdad wrote:

Is there anyone here who can say something about this?

Well, the dominant topic here is (unfortunately, for you) VAG-TDIs.

Unlike in online forums, here, people tend to only respond if they have reasonably reliable knowledge to share.
And CR professionals are (so far) relatively few in number, but perhaps a helpful answer will still come along.

Hmm, I'm not very familiar with this specific engine either, but I don't think the fuel system is the cause. It's probably still stored in the error memory because the tank was empty at some point, or something like that.
Is the service light on? Error: present or history?

Instead, I suspect a problem with the intake air/pressure, possibly due to a faulty mass airflow sensor or perhaps a stuck EGR valve.
'Low performance' is a relative term, or rather, it's very subjective.

Possible tests:
1. Disconnect the AGR connector (this likely triggers a diagnostic mode, but it will be resolved when the connector is reconnected).
2. Check the air intake system, specifically between the mass airflow sensor (MAF) and the turbocharger, for leaks (on the vacuum side).
3. Replace or verschandeln the LMM (laser module).

The loader probably doesn't have a VTG (Variable Turbine Geometry) turbocharger, but rather a standard wastegate.

In the cold weather, it's likely that the relocated smoke barrier is the reason, which aligns with the possible causes mentioned above.

Thank you for the answers so far!

It's quite frustrating when the so-called experts at Fiat and Bosch are clueless and I have to tell them what the problem might be!
The Bosch expert even told me, in response to my question of whether it could be the LLM, "It doesn't have one at all!"
What else can be said about that?

I'll probably try to replace the LMM myself.
Is there a way to test the LMM for defects?

I've noticed again that when the engine is cold, there's power available below 2000 RPM, so it drives normally. The warmer the engine gets, the more frequently the power cuts out. After about 5 km, it's very rare to have power available below 2000 RPM. After a long drive on the highway, nothing.

Regards,
Ralf.

I'm going to try a forum crossover. It seems this problem isn't an isolated case. At least I have similar concerns, and in my desperate search, I came across other people who are going through the same thing.
Perhaps some expert will eventually find the solution.

Here's the thematic crossover:
[url][/url]
[url][/url]http://www.motor-talk.de/showthread.php?threadid=1395010{MARKER}http://forum.langzeittest.de/read.php?f=122&i=5121&t=4872&v=f{MARKER}

Vintage, easy to use? Instructions on how to test can be found by searching the forums.

The problem is likely solved. There's a vacuum-operated valve on the engine that mechanically adjusts a plunger, which in turn controls a valve in the cylinder head (intake side). It's located directly in front of the driver's side on the cylinder head, and it's probably used for cold start regulation. The membrane inside the container often leaks, or, in my case, the plunger (made of plastic) is worn down on the sides, so it no longer seals properly against the membrane.
When the engine warms up, a valve likely opens to create this vacuum path. The container cannot maintain the vacuum pressure required for partial load adjustment (which is supplied via a line connected to the distributor at the front, near the three vacuum containers).
Replacing the battery isn't really a problem, but it can be a bit fiddly because it's hard to directly access the three small Torx screws on the bottom of the holder. To do this, the entire housing needs to be removed (which includes the oil dipstick and filler cap).
I first removed the canister and the holder, and then I manually adjusted the adjustment mechanism on the control unit (by hand) as if the membrane were being pulled. Although I couldn't detect any difference in driving performance between the extreme settings of the adjustment.

At the front of the vacuum manifold, I connected the incoming U-shaped hose (which normally connects to the large, wide distribution chamber) directly to the middle vacuum booster. The performance is immediately restored (good for testing).
I secured the dipstick and filler cap with cable ties.
Now, I'm going to calmly get myself a new can. The car is still running for now...
I hope this helps other people who are going through the same thing.

Regards,
Ralf.