Keine Leistung nach ZKD Wechsel / Passat TDI PD AVF (GELÖST) | Posts 32+

Good morning.

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Please create a PD log with the following parameters: 13-18-23, in the LL environment.

I'll do that this evening; I'll be back at the workshop then. We need to log the acceleration data again, specifically between 8 and 11.

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I don't know now what you consider to be the start of funding.

Unfortunately, I don't remember the exact name of the field, but it's definitely the second or third field in MWB4. According to VCDS, the target range is -4° to +2°. Mine is currently at 1.2° before top dead center (BTDC), while my friend's is at 4° BTDC. I'll check tonight to see what the field is actually called. Whether this information is significant, I don't know. However, there's a difference of 5° compared to a "working" AVF (Antivalentventil).

I brought the car to work today. Yesterday, we took a short family trip (about 40km each way). So, it still runs very poorly when cold... Once it's warm, it drives okay, but you really have to press on the gas to get moving, which is probably why the display shows increased fuel consumption. But I need to refuel today anyway, so I can give you more accurate information about the actual fuel consumption over the next few days.
What's noticeable is this jerking/vibration, especially in the higher gears under load, which is clearly visible on the gear knob.

Okay, so I have another opportunity to watch something tonight, if you have any suggestions, please let me know.

Regards,
Daniel.

Street_Rod wrote:

Quote: I don't know now what you consider to be the start of funding. Unfortunately, I don't remember the exact name of the field; it's definitely the 2nd or 3rd field in MWB4. According to VCDS, the target range is -4°...+2°. Mine is currently at 1.2° before top dead center (BTDC), while my friend's is at 4° BTDC.

The data in fields 2 and 3 are purely software-dependent AND depend on various factors such as engine temperature, ambient air pressure, torque demand, etc.
The target values in the headers of the log files or label files are essentially rough estimates across a handful of data points and therefore DO NOT provide any reliable information regarding whether something is okay or defective!

Evening.

Okay, here are some more logs: 8-10-11 in 3rd gear, approximately 1200-4500 RPM, and 13-18-23 in low range (LL). The first reading might have been taken before the engine was fully warmed up.

According to the MFA (manufacturer's fuel consumption data), it consumes approximately 9-10 liters. I filled up the tank completely today, and I will post the overnight fuel consumption figures in a few days.

Yesterday and this morning, it wasn't running well at all, and it was vibrating quite strongly under load and boost pressure. This evening, however, it ran much better again, and the jerking was also noticeably less, which I could feel by putting my hand on the gear knob.

Regards,
Daniel.

Street_Rod wrote:

So, here are some logs again, 8-10-11 in 3rd gear, approximately 1200-4500 RPM, and 13-18-23 in idle, and the first one probably wasn't fully warmed up yet.

The logs don't show me anything new: everything is normal except for the slightly low LuMa readings and the LD-TV.

What do you think about the PD Logs 13-18-23?

Hi there,
There must be a reason for the loss of performance.
Let's rule out the possibility that the catalytic converter, diesel particulate filter (DPF), or exhaust system is blocked, or that the brakes are stuck.
The compression is also fine, and the values in VCDS aren't particularly alarming.
Despite this, the engine runs sluggishly both during operation and sometimes when idling.
If everything seems to be correct, the next question is: which values are measured directly, and which are derived from other quantities?
The boost pressure is measured directly using a pressure sensor, and the same applies to the lambda (air-fuel ratio), synchronization angle, valve status, and beats per minute (BPM).
The amount of fuel injected is not measured directly, but rather calculated based on the opening duration of the PD valves. This requires correctly adjusted piston stroke and the appropriate upstream pressure at the PD element. Neither of these factors are detected by the MSG (Motor Steuergerät - Engine Control Unit). If these prerequisites are not met, the MSG will not detect an insufficient fuel injection amount.
Could it be due to this – that is, are the PID elements configured correctly, and is, for example, the supply line clear and not constricted?
hg
Herbert.

Herbert wrote:

Are the PD elements configured correctly? Is the supply line, for example, clear and not constricted?

In this context, I'm currently wondering if the supply pressure from the

Street_Rod wrote:

tandem pump creates pressure (even if it's at the lower limit) -

is sufficient even with maximum motor load.
Okay, so connect the pressure gauge again using that long pressure hose and attach it externally in a way that you can still see the scale from inside the car when the hood is closed. Then take a short drive and accelerate to approximately 4500 rpm in second gear with full throttle, while observing the pressure.
If that's not possible, connect a pressure gauge with as little damping as possible and bring the (warmed-up) engine to full throttle while stationary, exceeding 4000 rpm.

If the fuel pressure drops below the target value during periods of full throttle, there's likely a bottleneck somewhere in the diesel supply system. When driving, more fuel is injected, so any potential pressure drop would be longer and more noticeable than when the engine is idling.


I'm assuming here that the PID settings are already correctly configured.

Good morning.

The PDE elements were not fully disassembled the first time when the head was removed; only a basic adjustment (180 degrees) was performed. A silly question, but which specific supply line are you referring to? All the lines in the engine compartment between the supply and return lines, i.e., those leading to the DFI (direct fuel injection) and the tandem pump, are fine. Or are you talking about the line that comes from the tank? To be honest, I haven't checked that one yet.
Ich habe die Tage Gelegenheit noch eine neue Tandempumpe zu testen, wobei ich mir dabei keine großen Hoffnungen mach. Aber dann weiß ich das auch 100%ig und kann das evtl. ausschließen. Was mir nicht in den Kopf mag warum das Auto täglich besser läuft?!?! Meine Frau darf zur Zeit meinen 80er (Winter-)Audi fahren und ich hab eigentlich grad immer den Passat. Gestern Abend und heute morgen lief er wieder recht annehmbar und gut wie nie (seit das Problem nach ZKD Wechsel auftrat), auch das Ruckeln/Vibrieren wird spürbar immer geringer. Er zieht nach und nach wieder freier hoch. The consumption (according to the MFA - Multifunction Analyzer) also seems to be slowly returning to normal. By the end of the week, I'll know exactly what it really needs, after I've driven the 100 km.

Could the PDEs have been affected by some underlying setting? It's slowly becoming the only plausible explanation for me, even though I read these threads here.

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

While one of them was a VEP TDI, the problem was quite similar.

Let me start with a few questions:

Should all PDEs or only one be replaced in the AVF (Automatic Voltage/Frequency Regulation system)?
- What do you think about refurbished PDAs? There's a company at the auction house that deals with refurbished PDAs (I'm not sure if I can mention their name here), and they offer them for around €200 in exchange.
- Does the Diesel Mechanic Shop still have injector sleeves available? (I couldn't find anything on their website, although older threads suggest they used to offer them).

Danke u. Greetings.
Daniel.

I would like to see the PD log because I saw parallels between the symptoms and the case described here: /viewtopic.php?t=19461.
Those PD elements were finished.
I think you're not having any issues with fuel delivery. The air-fuel ratio values would then be tightly in the negative range. Your pressure drop log looks normal so far, except for the constant addition of over one milligram per stroke for cylinder 4.
Was the compression specifically on the 4th cylinder not lower than it was on the other three cylinders? So, there wasn't a difference of 5 bar?
The question is, after the initial adjustment for the PDE: first set to the lowest point (using a dial indicator), then turn the adjusting screw in the rocker arm shaft all the way in, and then rotate it back 180° and tighten it with 30 Nm of torque. This applies to all four. Otherwise, differences will arise that he wants to compensate for electronically.
The next question would be: Do all the valves open and close correctly? Are there any noises coming from the valve actuator? Hydros IO?

Street_Rod wrote:

Which specific return line are you referring to? All the lines in the engine compartment between the supply and return lines, i.e., those leading to the DFI and the tandem pump, are fine. Or are you talking about the line that comes from the tank? I haven't checked that one yet, to be honest.

I meant everything that has been touched since the engine last demonstrably had full power (so probably before the head gasket repair?).

Steffen W wrote:

I think you might not have a problem with the fuel supply.

The BIP values would then be tightly in the negative range. }However, all previous BIP logs were at idle, if I recall correctly? That's why my test suggestion is "fuel pressure at wide open throttle".
However, you are right to the extent that problems specific to WOT (Web of Things) should also be identifiable in WOT-BIP log data.
So, when both MWB 1 and 23 are logged simultaneously at full throttle, the RPM range is approximately from 1500 to 4500 RPM, preferably in 3rd or 4th gear.

Yes, all the BIP logs were in the LL directory.

"The compression is consistently high on all four cylinders, measuring 30 bar. When we removed the cylinder head for the second time, we also rotated the crankshaft manually, and all the valves opened properly; there was nothing unusual. The camshaft is okay and shows no signs of significant wear. There are no noticeable noises in the valve train, such as hydraulic lifter ticking; everything sounds smooth. We adjusted the pre-tensioning devices (PDEs) correctly; admittedly, not using a measuring tool, but as described in the manual, you can see if they're properly adjusted by checking how far down a wrench goes at their lowest point."
I should be able to run the logs again tonight.

Greetings.

Street_Rod wrote:

I should be able to run the logs again tonight.

Also, please check the MWB 7 to see if all the temperature sensors are providing reliable values: mainly to rule out that too cold diesel is constantly being reported, which could be causing a lack of power.

Hi there,

Quote:

That's a silly question, which specific return line are you referring to?? All the lines in the engine compartment between the supply and return lines, i.e., those leading to the differential and the tandem pump, are fine. Or are you talking about the line that comes from the tank? To be honest, I haven't checked that one yet.

The "distribution pipe" between the tandem pump and the common rail injectors in the timing chain housing. Did you remove the pump when replacing the timing chain cover gasket?
Stop exchanging information based on suspicion; it only introduces new errors.
Please check the actual temperatures as suggested above.
Also, also auch the fuel pump or its pressure.
In my opinion, there's a guide in the RLF that states (The PD experts know more).
- at least 7.5 bar at 4000 rpm,
- If located underneath, clamp the return hose and recheck.
- If the pressure remains below 7.5 bar, replace the pump.
- If 7.5 bar is reached: Leak at the high-pressure diesel injection pump between the inlet and outlet (seals).
If necessary, repeat the PDE settings as described above.
Also, set the Northwest synchronization angle to between 0° and 0.5° early. A slightly late setting can contribute to sluggish behavior.
hg
Herbert.

We removed the tandem pump when the head was taken off, and of course, we installed new seals during reassembly. We blew out the channels, which are the supply lines in the head, while the pressure drop eliminators (PDEs) were still outside.
According to the vehicle's service information (RLF), we checked the fuel pressure using a tool/pressure gauge from Audi. The pressure was at the lower limit (I know I wrote 7 bar, but it might have been 7.5 bar), so we didn't investigate further there, meaning we didn't try things like clamping off the return line. We adjusted the PDE (high-pressure pump) three times, and we can practically rule out that the adjustment is incorrect.
Okay, I did the logging as requested today (1-23-7 in 4th gear). I also refueled. The actual fuel consumption, considering a lot of short trips and several test/logging runs, is 8L per 100km. The MFA (Multi Function Display) shows an average of 10L. The MWB7 data seems to show normal values, although it's included in the log.

Greetings.

Street_Rod wrote:

I did the logs as requested today (1-23-7 in 4th gear). I also refueled, and the actual fuel consumption with a lot of short trips and several test/logging drives is 8L/100km; the MFA shows an average of 10L. The MWB7 readings show what I believe are normal values, but that's included in a log. Greetings

. The download "8-13-11.csv" shows me only a blank sheet. But it doesn't matter, because we already had 81, and 13 will anyway be frozen above certain quantity and speed thresholds.

MWB23@ shows lower values for cylinders 2-4 compared to idle speed, and notably so towards the maximum diesel injection quantity (Pmax), which I believe indicates a tendency towards issues with injector filling.
The discrepancy between the displayed fuel consumption and the amount of fuel actually added is moving in the same direction.

As a possible explanation for everything, I suspect there's an air leak somewhere in the main line, most likely between a hose section and the fitting where it's connected: this could explain the observed daily patterns related to the temperature behavior of the materials around the suspected air leak.

For testing purposes, please replace this text temporarily.
-> the hose section located directly in front of the tandem pump on the supply line.
-> somewhere in the feedback loop.
Observe the water flow through transparent materials, such as for aquariums, and with the motor running (possibly with short bursts of full throttle), identify where air bubbles are visible.
If everything constantly looks like flat beer, the explanation doesn't fit – or if the engine is delivering its usual performance again because you eliminated the air leak by installing the clear hoses.

After a long time, I can finally post the solution here...

The Passat had been stuck for the past two weeks, but now the car is running again, and it's better than ever – smooth, with full power, no jerking, and pulls nicely.

They were the...

*drumroll*

PDEs!

We had them disassembled again and sent to a Bosch service center through an acquaintance, who thoroughly inspected them. Three out of the four were not delivering the full fuel volume; the diagnosis was that the memory units were failing and the sealing material had hardened. They were then completely overhauled, meaning not just the injector nozzles were replaced.

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[Sarcasm on]Oh, those are definitely clogged and leaking because they were removed from the engine head.

That's enough about that... why this suddenly happened when the head gasket was changed remains a mystery. But I, or rather my wife, am glad that the car is running again!

Thank you all for your help! I hope this long thread proves useful to at least some of you!

Greetings from Bavaria.
Daniel.