Cooling temperature -10°C and boost pressure 0 bar at idle:

So, I've completely reassembled my Passat Variant 4Motion (year 2000, AFN 110hp) over the past two days and given it a second life. I've installed a new engine, pistons, timing belt, all bearings, a new turbocharger (130hp), a catalytic converter, a modified engine control unit, and a new front axle. Similarly, a boost pressure gauge, an oil pressure gauge, and an oil temperature gauge were also installed.

After a few initial issues were resolved, the error memory is now clear. However, I have 2 interesting features:

1) The Passat starts immediately, even with a cold engine. The idle is stable at approximately 1000 RPM, but the boost pressure gauge shows 0 bar. Coolant temperature display, VAG Com, group 007, value 4: -14.4°C.
2) The Passat runs for about 5 minutes, the engine is warm, the idle speed fluctuates erratically between 700-1000 RPM, and the boost pressure gauge shows 0 bar. Coolant temperature display via VAG Com, group 007, shows a value of -9.5°C. However, the instrument panel coolant temperature gauge displays exactly 90°C. ??????

Since I'm not a fan of electricity, I'm very careful when dealing with these things.
Since the engine conversion required disconnecting all the connectors, the problem might be located there.

-All coolant temperature sensors are new - green (G62) and the blue one.
-Unfortunately, expanding the windshield wiper linkage would also require disconnecting the connectors between the vehicle interior and the control unit.
- also climate control connector plugs.
- and also fan connectors.

What I actually still wanted to do is:
- Perform the basic ESP (Electric Servo Pump) adjustment, but according to VW, this cannot be done if the water temperature is -10°C.

According to the VW repair manual, I should replace the sensor (although it's new) and check the wiring between the control unit and the connector for a resistance of 1.5 ohms and for any loose connections.
"However, since I've seen the hundreds of pins on the control unit, and only the 4 connections on the coolant sensor connector (green), it will take years!"

Have you encountered these two problems before?

Yesterday, I took it for a short test drive in deep snow. The boost pressure reached 1.3-1.4 bar, and there were no error codes in the engine control unit.

Thank you for your opinions.

So, yesterday evening, after approximately 80 diagnostic tests, the fault was found. It was two resistors that were soldered in, which were falsely indicating extremely low temperatures to the control unit, causing the glow plugs to remain active for a longer period. It used to be a POEL vehicle.
Removed the resistors from the cable, and everything is working again...

The only thing I don't understand is whether the boost pressure is really 0 bar in idle for a TDI engine? Okay, with the VR6 compressor, I'm always around 0.7 bar, but with the TDI, it never goes down?
"I checked all the solenoid valves and all the hoses again yesterday, but I couldn't find anything."

Thank you for the information.

It's been taken care of... You just need to use the search function...

A general rule of thumb for the required pressure range of the display:
Up to the standard power output of 130 hp (without turbocharger tuning), a pressure of 1.5 bar is sufficient. Above that, a pressure of approximately 1.8 to 2.0 bar is more appropriate to clearly read any overshoots during turbocharger adjustment.

When selecting the instrument further, the suction range displayed initially seems illogical, as a diesel engine typically doesn't have a throttle valve.
However, even in TDI engines, blockages in the intake manifold can occur, and early detection of these blockages can explain a lack of power and, in some cases, prevent expensive damage.

No throttle body - no vacuum!

Okay everyone, now the VR6 is about to become a beast!

I've already completely rebuilt two cars (a Corrado VR6 with a supercharger and a Golf2 VR6 with a turbo), but this Passat TDI is going to drive me to my grave!

Data, facts, figures.

VW Passat Variant 4Motion, year of manufacture 02-2000 - engine code AFN, chassis number 246084 - transmission code EEP 30129!

"Purchased in September 2008, with all invoices. Has 4 cracks in the cylinder head. Professional conversion performed by "Vereinigte Werkstätten für Planzenöltechnologie" in 90584 Allersberg, starting at 22,610 km, costing 9,599 DM in 2001!"

Decision: Everything is being redesigned - Duration of renovation: 2.5 months.

Rebore the engine cylinder and install oversized pistons, stage 1.
new pistons
new bearings and seals.
New water pump + oil pump.
ESP needs to be recalibrated.
Have the fuel injectors adjusted to 0.216 and 220 bar.
New Turbo GT1749VA - 038145702G
Chip tuning for new components.
AGR deactivated using adapter plates.
Boost pressure + oil pressure + oil temperature display installed.
Exhaust temperature sensor installed.
All diesel lines and water hoses replaced.
new timing belt and tensioner.

Okay, and now for the problem:

1) Poor cold start behavior (10 seconds) without the two 2kΩ resistors in the coolant temperature sensor circuit.
2) Moderate cold start behavior (3 seconds) with two 2kΩ resistors as pre-resistors.
3) Warm start without a pre-resistor, only possible with a partially printed throttle pedal; requires 10-20 seconds of cranking.
4) Warm-up with pre-resistance possible only with partially printed accelerator pedal, 5 seconds.

Today I went to VW for the second time, and now I even helped work on the car myself.
- Transparent diesel line integrated in front of the ESP unit.
- Absolutely no air bubbles present.
- All screw-type hose clamps are tightened and checked! Errors excluded.
- with the gas cap open, no improvement - error ruled out.
- Completely re-adjusted the timing belt, checked the top dead center (TDC) position, and performed the input/output (I/O) calibration, followed by dynamic ESP adjustment.
- Tank is 3/4 full with diesel from September 2008 - no plant oil present! ok...
- Battery charged, full capacity, and 13 volts are present! - Error ruled out.
- Adaptation initial value performed on channel 5, increased.
- Adaptation: Preheating increases Channel 12 - from 32768 down to 32700.

What other options are available now?

- Chip tuning, yes? What does that have to do with starting?
- Are the fuel injectors not working correctly? Can I have it checked and re-evaluated?
- ESP failure after 100km? Why?

I believe the TDI isn't getting enough credit... that's just my gut feeling.
Because the simulation using resistance increases the preheating time and the fuel injection amount, it makes the engine start more easily!

When driving from home to the workshop, the boost pressure at full throttle is approximately 1.3-1.4 bar, and it pulls well... without any soot or smoke!

Thank you for the information...

A compression test was also performed on all cylinders, with pressures ranging from 25 to 27 bar.

Hi,

Even though you probably already found this out, a boost pressure of 0 bar at idle is perfectly normal.

Regarding your actual problem: It's possible that your chip tuning is faulty - have you tried using the original engine control unit? Otherwise, if you get a poorly made chip tuning system, you won't receive any support, because the person selling it is actually the one who makes that kind of thing themselves...

Best regards,

Jan.

Okay, that's a good indication that the problem lies with the electronics and not with my working methods! "How on earth can the chip affect the starting behavior when only boost pressure and fuel injection volume are modified based on engine speed?"

I don't have another original control unit...
The only thing that works is restoring the original dataset.

I'll reach out.

stiervr6 wrote:

How the heck can the chip affect the starting behavior, when only boost pressure and injection volume are modified based on the engine speed????

Well, if...
When tuning, the complete engine software is accessible to the tuner, including the display of diagnostic values, starting parameters, etc.
If one is not careful and does not have the necessary knowledge, (or if, for example, the tuner believes that the electrical sensor curve of the water sensor affects performance and therefore distorts it excessively), then "a few altered bits can end up in the wrong places," causing completely mysterious problems.

Okay, so it started at minus 6.5°C this morning. It took about 2-3 seconds, and then the Passat started smoothly, without any hesitation or rough running. The idle speed was approximately 1000 RPM. As if everything were perfectly fine...

After reaching the operating temperature of 90°C, the engine speed drops to approximately 850 RPM and then begins to fluctuate between 1000-700 RPM until it eventually stalls.

Okay, I'm going to disconnect the return line now and see if approximately 1 liter of diesel accumulates in about 1 minute. Perhaps the suction power of the pump (which is quite old) is no longer sufficient.

"And due to the new, improved compression, according to the Dieselschrauber error analysis, the starter motor might not be able to achieve the necessary speed anymore due to its age (211,000 km - carbon brushes). However, removing and replacing it is difficult on the 4Motion model due to the lack of space and the amount of work involved. I'll probably leave that for later, because if the Passat stalls while idling, it's likely not related to the starter motor..."

Okay, check the part number on the ECU and then use a diagnostic tool to see what number it shows. I think what the others are saying about the chip tuning is a very promising lead. A friend of mine also had his ECU returned by a tuner with a "GF" ending, and it turned out to have a "GN" ending. This means that if they installed different software, it can significantly change the starting behavior, including the idle speed and fuel mixture. But does it run well now? Or is there a lack of power? Or what's the situation?

If the ESP has been serviced, the manifold frame may not be properly installed.
You can find instructions on how to verschandeln MSG (monosodium glutamate) there, and it also describes the basic settings. Just quickly read off the amount while it's running.

I spent another night in the workshop, but this time I went a step further:

@T3surfer:

It looks like you hit the jackpot.

I once connected a Spartan VAG com device and read out the "Motorwerte" (engine data) group 2 and 3 after starting up a Passat that had been difficult to start (requiring half-throttle and 20 seconds of cranking).

Conclusion: 30mg/h and 0.5 volts.
Therefore, a significantly leaner mixture!

Okay, I tried to adjust the VP37 quantity setting device according to the instructions, and I almost lost my mind because of how sensitive the component is! It's not measured in 1/10mm, but in 1/100mm, and it's impossible to adjust it with perfect accuracy using mechanical means.

"Now, it no longer shuts down at operating temperature, and although the idle speed is between 750 and 880 RPM." Of course, I couldn't accurately set the mg/hub because the values vary from 2.0 to 7.4 mg/hub - that was the best I could do.

However, something has caught my attention, and I'm quite annoyed about it. I bought new 0216 nozzles with their corresponding holders and had them adjusted. But when I log in and click through the blocks in the second row, I see this:
Cylinder 1, 0.
Cylinder 2: 1.88.
Cylinder 3: -1.88.
Cylinder 4, 0.

That can't be right!

,,,,,,,,,,,,,Engine speed, Injection quantity, Model. Piston Displacement, Coolant Temperature, Cylinder 1, Cylinder 2, Cylinder 3, Cylinder 4.
TIME,,,,,,,,,,,TIME,861-945,3-9,1.35-2.10,80-110,TIME,-2 to +2,-2 to +2,-2 to +2,-2 to +2
MARKER, STAMP, , , , , , , STAMP, /min, mg/R, V, °C, STAMP, mg/R, mg/R, mg/R, mg/R
,,,,,,9.15,882,2.0,1.600,84.6,0.02,0.14,1.88,-1.88,-0.07
,,,,,,10.03,861,3.0,1.660,84.6,9.59,0.14,1.88,-1.88,-0.09
,,,,,,10.91,882,2.4,1.640,84.6,10.47,0.07,1.88,-1.88,0.00
,,,,,,11.79,861,2.8,1.660,84.6,11.35,0.19,1.88,-1.88,-0.14
,,,,,,12.65,840,4.6,1.660,84.6,12.27,0.12,1.88,-1.88,-0.24
,,,,,,13.49,756,7.4,1.740,84.6,13.09,0.19,1.86,-1.88,-0.16
,,,,,,14.37,777,7.6,1.780,84.6,13.97,0.31,1.86,-1.88,-0.24
,,,,,,15.25,777,7.4,1.800,84.6,14.81,0.19,1.86,-1.88,-0.14
,,,,,,16.12,798,5.6,1.620,84.6,15.69,0.12,1.86,-1.88,-0.07
,,,,,,17.00,777,7.4,1.720,84.6,16.56,0.26,1.88,-1.88,-0.24
,,,,,,17.82,798,6.2,1.760,84.6,17.43,0.26,1.88,-1.88,-0.16
,,,,,,18.70,819,4.6,1.700,84.6,18.22,0.21,1.88,-1.88,-0.12
,,,,,,19.58,798,5.6,1.760,84.6,19.10,0.24,1.88,-1.88,-0.21
,,,,,,20.42,882,2.8,1.660,84.6,19.98,0.31,1.88,-1.88,-0.24
,,,,,,21.30,861,3.0,1.660,84.6,20.86,0.14,1.88,-1.88,-0.09
,,,,,,22.16,840,4.4,1.640,84.6,21.74,0.31,1.88,-1.88,-0.26
,,,,,,23.00,798,5.8,1.640,84.6,22.56,0.24,1.86,-1.88,-0.19
,,,,,,23.88,819,5.8,1.660,84.6,23.44,0.28,1.86,-1.88,-0.24
,,,,,,24.76,777,7.4,1.720,84.6,24.32,0.21,1.86,-1.88,-0.16
,,,,,,25.64,798,5.8,1.620,84.6,25.20,0.19,1.86,-1.88,-0.16
,,,,,,26.52,777,7.2,1.720,84.6,26.12,0.16,1.86,-1.88,-0.14
,,,,,,27.38,777,6.6,1.680,84.6,26.96,0.14,1.88,-1.88,-0.14
,,,,,,28.22,798,5.4,1.720,84.6,27.78,0.19,1.88,-1.88,-0.12
,,,,,,29.10,798.6,6.2,1.760,84.6,28.66,0.19,1.88,-1.88,-0.14
,,,,,,29.94,882,2.0,1.620,84.6,29.50,0.09,1.88,-1.86,0.00
,,,,,,30.80,819,4.4,1.660,84.6,30.38,0.14,1.88,-1.88,-0.12
,,,,,,31.64,777,7.4,1.780,84.6,31.20,0.21,1.86,-1.88,-0.19
,,,,,,32.56,840,3.8,1.620,84.6,32.08,0.14,1.86,-1.88,-0.09
,,,,,,33.44,840,4.4,1.640,84.6,32.96,0.19,1.86,-1.88,-0.14
,,,,,,34.28,798,5.8,1.620,84.6,33.84,0.16,1.88,-1.88,-0.14
,,,,,,35.20,840,4.4,1.640,84.6,34.72,0.14,1.86,-1.88,-0.09

So, the nozzles aren't working well and need to be adjusted again, right?

stiervr6 wrote:

Therefore, the nozzles are not working well and need to be adjusted again, right?

It sounds like it could be the injectors, but in an extreme case, it might also be the ESP (Electronic Stability Program).

Given that you're talking about significant fluctuations in the LL speed, it sounds to me like the ESP might be worn out. Most likely due to the PÖL operation. (However, the VP37 ESPs are also likely to wear out eventually, even in purely diesel operation.)

Where did you buy the nozzles? Were you present when the pressure was being adjusted, and did you see the print?

Regards,
Guste.

I still wouldn't rule out the software, as a crucial error can be made when adjusting to the larger nozzles, which could trigger such a vibration. I've also had a motor with that problem before.

After the software issues were resolved, everything was quiet.

Tip: Reset the STG (Engine Control Unit) and swap or revert the EEPROMs to their original configuration.

Here's the to-do list:


"I just spoke with the nozzle specialist, and they are re-inspecting it and will let me know... unfortunately, the whole process, including shipping, will take about a week! Of course, it's free. I will also request that they send me a picture." Then I will check the values again using VAG com.

2)
I also consulted with a specialist who services ESP (Electronic Stability Program) systems, and he confirmed that there was a significant amount of buildup in the form of deposits, but no scratches or damage were present. He says it still looks good, and if it's not producing enough pressure, I usually notice it while driving – there's no power.
I don't think I'll be expanding that anytime soon...

3) Chiptuning is way down on my list, because they're really professionals with a ton of knowledge... He modifies all kinds of cars in Southern Germany, like those from ***, MTM, etc.
But the possibility exists...

Unfortunately, with this SUPER winter weather, I have to park my Passat 4 Motion in the garage and wait it out, which is very frustrating. How often do you get the chance to really put the all-wheel drive to good use?