1.9 TDI VP37 Engine Misfire After 20 Seconds

Hello,

After reading this forum for what feels like an eternity, I'm now also the proud owner of a VCDS system, and this is my very first post.

Vehicle:
A4 B5 Avant, 8D5, 1.9 TDI engine (engine code: AVG), 5-speed manual transmission (transmission code: EEN), 254,000 km.

Background:
My partner got a new car this year, and I took over her A4 in exchange. I want to use it as a commuter car, so I'm in the process of getting the technology up to date.

What has been done so far:
- Original turbocharger replaced with a GT1749VA.
- Original fuel injectors replaced with 0.216 injectors from Dieselsend.
- Equipped with an 11 mm pump plunger and partially re-sealed (I say "partially" because the sealing for the flow control valve was intentionally not replaced, as I wanted to avoid the "uncertainty" of a potentially misadjusted flow control valve in this "engine rebuild" project).
- The engine was 90% disassembled; the crankshaft and pistons remained in place, while the rest was overhauled, replaced, re-sealed, and re-bushed.


Current status:
On Saturday, there was the first attempt to start the engine. The oil, coolant, and fuel were pre-filled, the system was bled, and the engine started immediately. Today, after fixing some minor coolant leaks, the fuel injection was adjusted, and everything is going well so far, except for this one problem.


Problem:
Now, regarding the problem: After starting, the engine runs smoothly for only about 20 seconds, after which it begins to run erratically.

If I then turn off the engine and restart it after, for example, a 1-minute pause, the same phenomenon occurs.

The problem persists, regardless of how long the engine runs.

No errors are registered in the error memory.
I would classify the gas intake (on the lift, as it's not driveable) as OK. The engine revs up nicely, although you can still notice this "uneven" engine running even at higher RPMs.

Before I assemble everything on the front of the car (e.g., the service panel, bumper, covers, etc.), I'd like to make sure the engine is in good condition.

Attention: The engine control unit software has not yet been adjusted for the injectors, pump, and turbocharger; currently, everything is still running with the original software.
Currently, the vehicle is also not roadworthy because some work remains to be done on both the front and rear axles. Therefore, I cannot offer a test drive or transport it to a chip tuner.


Now, I'm asking for your help.
I logged some relevant parameters while the engine was idling. Unfortunately, I lack the expertise to properly evaluate the data.

The only thing I could determine is that the motor speed was stable and consistent from the moment the engine started until the error occurred; after that, it fluctuated, which I could also see in the logs.

If the root cause of this problem is "just" the unadjusted software, I would be relieved and could assemble the front panel, etc., with a clear conscience.

Please review the logs; I hope I've caught the correct MWB (Material Waste Bins).
I've also connected a car scanner to it.


Okay, here's the translation:

Thank you.
Best regards, Stefan.

Hello,

The reason is an excessively high actual fuel injection volume, which the ESP control system cannot handle properly.

Adjust the ESP (adjust the upper part of the control unit on the pump) so that you achieve an injection rate of approximately 3.5 - 5.0 mg/hour with the engine at operating temperature.

Simple test: If you experience the unstable idle issue, try using large electrical components like the rear window defroster for a period. If the problem disappears, it suggests that the issue might be related to the power supply or voltage regulation.

/viewtopic.php?t=165&highlight=unstable+idle

Hopefully, you had the DHK adjusted at Dieselsend.

Best regards, Rainer.

Hello Rainer,

I was hoping for such an answer.
Thank you very much for the solution and the tips.

I'll try it out next weekend.


Yes, and I've already finished setting up the DHK and purchased it ready for installation.

Thank you again.
Best regards, Stefan.

Hello,

Here is the feedback regarding the topic:

Since I needed to adjust the point machine to fix the problem, I also decided to replace the corresponding seals on the point machines, so I took them down and put them back up.

After adjusting the MSW (presumably a type of engine control unit) and setting the injection amount to the current value of 3.8-4 mg/H, the engine ran smoothly and with a stable RPM.

Thanks again to Rainer!

Best regards,
Stefan.