ASZ starts warm, runs poorly - what could it be?

Hello everyone,
My social security office is constantly bothering me, and it seems like there are always small repairs that need to be done. After I had already replaced the thermostat and the transmission fluid, and I thought all the work was done, the fuel pump is now showing a new problem.
"When the engine is warm and I try to start it, it immediately dies. Normally, the engine starts right up without any hesitation, even when it's warm. But in this case, it dies immediately. This happens twice in a row, and then on the third attempt, it runs. What could be the problem?" Temperature sensor or camshaft sensor?

I would appreciate any help.

Thank you and best regards.
Reuselkopp.

You can rule out a temperature sensor by disconnecting it (then the system will assume...).
The engine is 'cold' and behaving accordingly.
Otherwise, it sounds almost like WFS.
Error memory?

Best regards,
Micha

Hello,
WFS is different; in that case, the engine runs for 1 second and then shuts off. But here, it starts briefly and then shuts off again. I can try unplugging the cable, but it doesn't always happen.
Error memory is empty.

Hi,

Either the water pump failure sensor is triggering (it's stored in the engine control unit's error memory), or there's air in the cylinder head that's entering the common rail injectors during the brief running period, causing the engine to stall.

Best regards, Rainer.

Hello Rainer,
If there was air in the cylinder head, wouldn't the cold start also require a long cranking period?

If the "leak" only occurs when the engine compartment or the tandem pump is hot, then no. If it always occurs, then yes.

Does the engine also stall if you turn it off when it's hot and then start it again 10 seconds later?
If so: Likely not a fuel or air problem.

Autoscan, fault memory?

Best regards, Rainer.

Hello,
I tried restarting the test after 10 seconds, but then the engine starts.
Today, it stood for about 10 minutes, and sure enough, I needed three attempts before it started.
How can you determine if a PDE (Pressure Drop Event) is leaking? Is there a test for that?

Regards,
Reuselkopp.

Hello everyone,
"After I had the head gasket replaced and have now driven approximately 700 km, I experienced the same problem with the cold start today as I did before the replacement. Subjectively, I would say that the engine runs better after the replacement, and the fuel consumption has also decreased slightly. I haven't noticed any increase in engine oil consumption, and the long-term relative road noise (LLRR) is 0.00 for cylinders 1 and 2, +0.50 for cylinder 3, and -0.50 for cylinder 4." In measurement block 23, all PDEs are within the range of 0-15.
I performed the change following the Audi instructions found online and the PD adjustment thread here on the forum. I don't think I made a mistake with the change.
Where else could the problem lie? Could it be the tandem pump? Or is the return line leaking? Or perhaps one of the sensors?

Regards,
Reuselkopp.

Hi everyone, does anyone have any other ideas?

Best regards, Reuselkopp.

If you establish a diagnostic connection to the engine control unit (ECU) during a warm start/shutdown, does the connection remain active (indicated by a rotating line in the top left corner of the ECU information display) and then disconnect?

Best regards, Rainer.

Hello, I don't know. I would have to check, but the problem is that the issue of it not starting only occurs very sporadically. What's the relevance of the connection dropping?

Best regards, Reuselkopp.

Connection lost: The motor controller has rebooted and/or is experiencing power supply issues.

Hello everyone,

I would now like to provide feedback on what caused the poor starting behavior. After the starter motor failed to start the car properly even with a perfectly good battery on cold days, I decided to replace it. I found a very well-maintained starter motor for €25 from a recycler on an online marketplace, and sure enough, the starter motor now starts the car immediately, both in cold and warm conditions. The problems have completely disappeared.

Hopefully, I'll be spared any further repairs for now, otherwise I'll have to start thinking seriously about getting a G7 variant again.

Regards,
Reuselkopp.

Thank you for your feedback!