Re: 1.9 TDI experiencing rapid power loss, severe knocking | Posts 16+

Hello,

comco wrote:

My Octavia 1U 1.9 TDI's chip tuning resulted in a drastic decrease in performance. V-MAx only reaches 120 km/h at full throttle, noticeable engine knocking at partial/medium load, not a Russian model. The engine is only revving up painfully now.

If the valve is okay and clean, and it's receiving power, then the problem might be with the injector itself, just like it was for me last year (the symptoms were definitely the same as yours).

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The pump was running on fuel oil and, due to a setting that was too early, it was operating outside the normal operating range, but this seems to happen even with the standard diesel setup.

Best regards, Uli.http://fmso.de/forum/messages/825060.htm{MARKER}

Just for clarification: Even if the SV valve were electrically defective and stuck in the closed position, or if the strainer or holes were clogged, it is impossible for the injection timing to be greater than 20 degrees before top dead center (BTDC). The internal pressure of the pump at idle is simply not high enough to cause that. (Assuming the static timing is not completely incorrect). This suggests to me that the SV piston is seized in its earliest position. That can then be relatively easily verified...
And before that, let's rule out the needle lifter.

Hi,

The VP 37 is partially disassembled (distribution/high-pressure section) to the extent possible while it is still installed.
Mechanical condition is excellent, no contamination or residue.
The expected or suspected crack or fatigue in the high-pressure section did not occur.
The spray nozzle looks great visually, and it will be tested for functionality in another vehicle tomorrow.

The complete disassembly will be done over the weekend, provided that it turns out the fuel injector in the other vehicle is working correctly.

Can the metering device be controlled via VDCS? Would it then be possible to observe it directly at the shaft? This one is "free" and can be rotated fully without obstruction, and it automatically returns to its starting position.


I have uploaded another 004 log.

Thank you very much to everyone who has helped me with their advice.

Bye.

Jürgen.

Hi,

Quote:

Even if the SV valve were electrically defective, stuck in the closed position, or if the strainer or holes were clogged, it is impossible for the injection timing to be > 20 degrees before top dead center (BTDC). The internal pressure of the pump at idle is simply not high enough to cause that.

Incorrect. That's exactly what happens during actuator diagnostics.

Quote:

so the VP 37 is partially disassembled (distribution/high-pressure part), as much as was possible while it was installed. Mechanical condition is excellent, no contamination or residue. The expected or suspected crack or fatigue in the high-pressure section did not occur.

This is pointless tinkering. The way you're working is introducing more errors, possibly even into another vehicle. It's obvious you've already removed the quantity control valve. A new ESP costs approximately 900 euros.
hg
Herbert.

Herbert wrote:

This is pointless tinkering. With your working method, you are introducing further errors, possibly even into another vehicle.

Partial agreement: While I understand the hardware-based control of the SV, I do not understand the decomposition of the MSW.

Quote:

Part number: 038 906 018 P Component: 1.9L R4 EDC, part number G00SG, 1629. Bitte gib den Text an, den du übersetzt haben möchtest. Sure, here is the translation of the text from German to English: "1 error found:" 00550 - Injection start control. 17-10 - Rule difference - Sporadically

In the event of an interruption in the SV circuit, there should normally also be a corresponding error entry.
Since the engine has been chipped, it's possible that the electrical valve timing control system may have been damaged as a side effect.
Option 2: Transition resistances somewhere in the servo circuit that still allow the test current to pass (hence no electrical fault indication), but severely restrict the operating current, leading to such a late adjustment that regulation is no longer possible.


In the 1-3-23 log, there is no indication of an EM value higher than 25 mg anywhere, despite the fact that the target value for LuMa is 850 mg, the actual LuMa value reaches over 900 mg, and the target value for LD is 1989 mbar. Normally, this means full throttle and a properly functioning mass airflow sensor (MAF), which would require injecting significantly more than 25 mg of fuel.
From this perspective, the performance degradation now smells like a fallback mode triggered by a detected software vulnerability, and then we would have a common cause for all the symptoms.

Hi,
In the last log, you can clearly see the sporadic issues with the injection start control. Occasionally, the target and actual values align, but then the adjuster suddenly jumps back to its maximum early setting, even with full activation from the engine control unit (ECU). A mechanical fault is unlikely in this case; a disruption in the electrical system is more typical. That's exactly what the error message says.
The next measurements would ideally have been taken directly at the valve (resistance, voltage, and how the valve responds).
Currently, the first task for our technician is to adjust the quantity control valve on the ESP (Electrical Submersible Pump) that is not functioning correctly.
Ulf, do you think the suspiciously low emission values could also be related to the chip tuning? She doesn't fit in with the LM and the LD.
hg
Herbert.

Has the voltage supply to the SV valve ever been measured?

Herbert wrote:

Ulf, do you think the suspiciously low EM (electromagnetic emission) could also be related to the chip tuning? She doesn't fit in with the LM and the LD.

Nothing is impossible...
But then the tuner would have had to confuse "more" and "less," and I don't think anyone is that clueless.
Furthermore, the problem likely didn't start exactly when the tuning was done, but sometime later.

"I think the 25 mg as a maximum effective dose is a pretty good fit for the emergency situation." Somewhere in every (TDI data set I'm familiar with), there's a kind of "failsafe torque limit" that operates at this level, if I recall correctly.

Herbert wrote:

It seems you've already removed the quantity signaling device.

Hi Herbert,

Oops, I'm also staying away from MSW (presumably a specific software or system), which is why I asked if a corresponding actuator analysis can also be performed using VCDS. Only the high-pressure section and the safety valve are installed.

Furthermore, I eventually HAVE to start finding and fixing the error. The wiring can largely be ruled out.

The LMM (likely referring to a mass airflow sensor) is only about < 10,000 km old and wouldn't cause such a significant loss of power.

If no objections are raised, I will proceed as follows:

The SV will be tested on another vehicle where the timing belt will be replaced this weekend.

If there are no errors, my MSG (Modular System Gateway) will be installed in the other vehicle (the WFS - Wireless Feature System - will be bypassed using my ignition key transponder).

If it works, I will remove the injector control valve piston from my vacuum pump.

If the injector control piston is free-moving and undamaged, a further rigorous test of the two injector control cables is performed. This involves using a 21-watt bulb as a load and twisting the cables along their entire length, from the MSG connector to the VP connector, pins 9 and 10.


Bye.

Jürgen.

comco wrote:

I'm also not using the MSW, which is why I'm asking if a corresponding actuator analysis can also be performed using VCDS. Only the high-pressure section and the solenoid valve (SV) are installed.

Depending on the starting temperature (?), the MSG (presumably a control module) performs a test of both pressure limits every time the ignition is turned on, which can be heard as a click-click sound coming from the pump.
I am not aware of any specific actuator analysis for the MSW that can be performed using VCDS.

Hello Jürgen,

Is the fuel return line and the throttle free?

Best regards, Rainer.

Hi Rainer,

Return shipping is free, but where can I find the throttle?

Do you mean the check valve in the return connection? (see picture)

When I apply slight pressure (with air), it slowly escapes from both holes. When there is a vacuum, the check valve can be heard clicking, and the vacuum decreases proportionally to the decrease in pressure.

Through the left bore, I can see a spring and a piston that is currently covering the right bore on the 17mm flange.

The piston has a free travel distance of approximately 2 to 4 tenths of the distance from the right end stop until it contacts the left-side spring.

Bye.

Jürgen.

Hi,

While further disassembling the valve block, some small pieces of aluminum debris came loose during the removal of the adjustment piston cover.
The set screw is broken; it looks like something hungry was gnawing on the aluminum -> see the picture.
I suspect this will be the root of all evil. The piston was stuck in its resting position.
The cylinder bore has minor areas of sticking, but the diameter is still within the tolerance range.

What's next?
A new valve plate, or an attempt to hone the cylinder bore and install a new piston.
I tend to favor attempting a repair, also for cost-related reasons.
Are there any experiences with this yet?


Bye.

Jürgen.

Unfortunately, this type of damage is quite common. Now it depends on how severely the housing is damaged. If Bosch sells individual parts, I would replace them, including the spring. Otherwise, as you mentioned, cleaning it and making sure it moves freely is the cheapest solution. However, the reason why the piston slams against the wall and literally breaks out of its housing is still a mystery to me.

Uli S. wrote:

It could also be the injection valve control piston itself that is faulty, just like it was for me last year (the symptoms were definitely the same as yours):

Hi Uli,

Did you successfully replace the spark plug back then, or did you just verschandeln it?

According to Bosch ETK, the piston is available as a single part.
I'm just going to the nearest Bosch service center in Steglitz.

Bye.

Jürgen.

Hi,

The VP (variable valve position) unit has been reassembled, installed, and is now sealed.

The engine starts without any problems, but the expected performance increase is not achieved, and the fuel injection still always begins at 27.9 degrees before top dead center.

Herbert and Ulf had already mentioned that there might be two different issues, especially considering the low injection volume.

So, if the internal pressure of the injection molding machine is too low, then the new injection unit piston may not be able to overcome the spring force, as I understand it.

Due to the lack of a suitable measuring instrument, I measured the reflux volume, which, according to Uli S.'s instructions, should be approximately 0.2 liters/minute at idle.
After 20 seconds of idling, I was already losing about 0.5 liters.

I assume that only the combination of the throttle/pressure relief valve located in the return line determines the maximum internal pressure of the vacuum pump.
Is the internal pressure of the vacuum pump always too low if it is defective?

I cannot rule out a defect in the wing cell pump, as the flow meter, which I did not touch, made further disassembly impossible.

The new injection molding machine cylinder operates smoothly and without any sticking, and it was pressure-tested multiple times with compressed air before assembly to verify its functionality.
The solenoid valve functions as expected when 12 volts are applied, and the opening/locking mechanism has also been tested with compressed air. The SV (Steuergerät/control unit) also makes an audible clicking sound during the actuator diagnosis.

Bye.

Jürgen.