Audi A4 8E AVF: Warm Start Problems

Hello,
I'm having the following problem:
"When our A4 was cold, it would always start after the first rotation of the crankshaft, even in temperatures as low as -10 degrees Celsius."

A week ago, the problem started where the car wouldn't start when it was "lukewarm," even after multiple attempts of cranking for 5 seconds each time. However, it would start without any issues when it was cold.
I then drove the car to our local mechanic. The master mechanic literally said, "You know, the starter is broken. If it's not spinning fast enough and drawing too much power, I can tell you for sure if it's the temperature sensor."
Okay, we replaced the starter motor (with one that had 30,000 km on it) and the sensor near the fuel injector, but that didn't even begin to solve the problem. The "new" starter motor spins noticeably faster, about 50-100% faster, but I broke down again yesterday.
This morning, the car drove without any problems.

It can't be the fuel vent; the same thing happens with the cap open.

I just rolled down the hill near the house to try and start the car. When I used the starter, it sputtered and started after about 5 seconds (while stationary), and it had about 3 misfires in the first few seconds. However, the engine then ran smoothly. When I rolled it down the hill, it started immediately.
I also believe that since the ignition coil was replaced, the engine's idle speed has increased by approximately 100 RPM, to just above 900 RPM.

Error memory is empty.
No noticeable loss of power, although I didn't drive at maximum speed.
A curious incident: A few days ago, while still using the old starter, I drove off the highway, and the engine stalled in the middle of the exit ramp at approximately 2500 RPM under acceleration. It wouldn't start afterwards. I let the car roll to a stop and then walked to my destination. Later that evening, it started without any problems, and I drove back home through the city. The car has never stalled before.

The wiring harness in the driver's door was also damaged, which I repaired today, but it didn't affect the error. All fuses are okay.

Regarding the car:
Audi A4 8E Avant 1.9 TDI, engine code AVF.
6-speed switch.
Timing belt replaced 10,000 km ago.
Mileage: 230,000 km

"The mechanic suggested a compression test, but said he couldn't do it himself 'because I don't have the adapter for this Audi; I have adapters for everything else, but not for this one.'"
What might such a test cost?
I would appreciate any further information.
Regards,
Artur.

It sounds more like a problem with the power supply from the engine control unit. -> Engine stalls while driving, occasional warm start problems.

Try searching for 'Relais 109'. It might have a different name where you are, but it does the same thing.

Best regards, Rainer.

Hey,
Sure, no problem.
I'll try to locate the relays and, if possible, check them.
We just checked the battery, and it's reading 12.7 volts. When the engine is running, it's reading 14.2 volts.
Best regards,

Hey,
The search results indicated that relays 219 and 167 were associated with the AVF and relay 109, respectively, and that these relays were reportedly causing problems for various users.
However, I can't find the location of these relays to check or replace them. Can anyone help me with that?

"The car broke down on me again today, after driving about 3km uphill at speeds of 140-160 km/h. It happened when I pressed the clutch, meaning it couldn't maintain idle speed. Luckily, I had enough momentum to restart it."

Regards,
Artur.

Hello,
I've now replaced relay 219, but unfortunately, it didn't make any difference, just like changing the diesel filter.
We're really starting to get desperate here.

Does anyone live near Castrop-Rauxel, have a diagnostic device, know how to use it, and have some spare time? I would, of course, be willing to pay a small compensation for their time.
Regards,
Artur.

The error has been found.
The gasoline content in the fuel was unusually high.
It's bad enough that we didn't come up with that idea ourselves.
Best regards and thank you for your help!

a.tec wrote:

The error has been found. The gasoline content in the fuel was unusually high. It's bad enough that we didn't come up with that idea ourselves. Greetings and thank you for the help!

Und wie kommt das? Hattest du dich an der Tanke geirrt oder hast du diesen Mist getankt? Branded fuel?

It would be interesting to know. If you've drained the coolant, I would recommend replacing the Difi filter again and adding a little 2-stroke oil (1 liter per tank, just once).

See you later.

Quote:

The gasoline content in the fuel was unusually high.

That must have been a pleasant engine noise.

Hopefully, your PD elements haven't been eaten.

Best regards, Rainer.

We usually always get our fuel from a HEM station around here, but after 6 weeks, it's no longer clear who made a mistake.

We recently replaced the filter, and now we've tipped it over and filled it with diesel. The engine sounded completely normal, which is strange. I only thought I heard a slightly elevated idle speed. There's no loss of power or misfiring. The fact that it stalled while shifting at 160 km/h now makes sense. It started again when it slowed down... poor machine!

"Silly question, but what would using 2T oil do?"

a.tec wrote:

Stupid question, what would that do with the 2T oil?

In my opinion, 2-stroke oil belongs in 2-stroke engines and nowhere else.
So far, no one has been able to explain the benefits to me in a way that makes physical sense.
I also don't think that a single liter will make a difference.
Either the PD elements were consumed, or they were not.
That wouldn't fix the elements either.

If a small amount of gasoline gets in, they won't immediately break down. The only thing that happens is that steam bubbles can form in the warm engine, and the pumps can't move anything if they're filled with steam bubbles.

Check your in-tank fuel pump. If the engine stalled while under load, this, in combination with fuel, could indicate excessive vacuum in the fuel system -> which promotes the formation of air bubbles.

Tagessuppe wrote:

a.tec wrote: Stupid question, what would that do with the 2T oil? In my opinion, 2-stroke oil belongs in 2-stroke engines and nowhere else. So far, no one has been able to explain the benefits to me in a way that makes physical sense. I also don't think that a single liter will make a difference. Either the PD elements were consumed, or they were not. That would not repair the elements either.

"No, of course, you can't really fix anything, but as long as there's gasoline in the diesel, it lacks lubrication, and you can add external oil to compensate for that, as long as you don't have pure diesel in the tank."