A3 TFSI 2.0T erratic start/hesitation with low RPM mostly on warm starting

[ajTonyCM]

Hey Fellow Audi Drivers,

I have an issue with my A3 2011 2.0T (85K miles) for about a year now. It happens only in the warm season (I live in Illinois) or/and at warm starts.
Right after the ignition, the engine sometimes hesitates and RPM drop below normal 800 to 550-600 and lower. With this hesitation, the engine might shut down.
I can rev it up with no problem, and after idle sets on 800 RPM, the car runs fine with no issues. There are no errors with VCDS, and the car runs perfectly fine.

Please see the videos.

https://youtu.be/NmQ_GQxVAFA

https://youtu.be/kv5VBtyK9fs

This is definitely not normal.

Ignition coils, spark plugs, fuel, air filters are all new. I also cleaned the MAF sensor recently, checked for vacuum leaks.
I only use 93-premium gas from Costco and put Motul 5W-40 in the engine.

Today I checked all temperature sensors with VCDS, and all measurements are reasonable. When starting the car (warm) for Engine Coolant and Oil, it shows 80 – 100 C, Air temperature sensor reading is in the range 50 – 60 C.

What else could it be?
Bad fuel, leaking injectors, carbon buildup, HPFP?

Appreciate any ideas/help!

[ajTonyCM]

Ok, I ran VCDS at engine start hesitation to check what is going on in cylinders and see if the injectors were leaking. It appeared that all injectors were fine as "fuel rail pressure" was going up consistently with switched ignition after shutting off the engine. I noticed misfires in cylinder 4, and after changing the ignition coil, the engine starts fine, no issues so far. It looks like the 06E905115E "type R" coils I purchased last year are defective. I ordered four brand new genuine ones 07K905715G, latest revision.

[ajTonyCM]

After regapping spark plugs and putting the latest revision ignition coils, this happens not so frequent but still persists.
Could it be a clogged intake manifold or a weak HPFP?

Again, after startup car runs and accelerates normally with no issues or codes.

[ajTonyCM]

Did the intake valve cleaning with CRC GDI.

Noticed that when disconnect air temp sensor it starts much better. Replaced the intake air temperature sensor (the one above throttle body) with the new one. Did not help at all.

Any ideas where else to look?

[Stazi]

Probably needs a thorough carbon clean with the intake manifold off.

[Ronsav98]

Suggest to replace the PCV assembly. Possibly stuck open. Notice an increase in oil consumption?

[ajTonyCM]

To all future readers, the issue was with the LPFP (low-pressure fuel pump), a common problem with GTIs and A3s. I read about this issue everywhere; people update all kinds of things, do carbon cleaning, HPFP, cam followers, even ECU, but nothing of that helps. When purchasing an upgraded LP fuel pump, ensure you get the right one with your VIN, as there are some different options. Mine was 1K0 919 051 DE, got from eBay.

[ajTonyCM]

I diagnosed it with VCDS by checking the LPFP load (don't remember the exact group number).