AJM startup problem

Hello.

I'm having the following problem with my Volkswagen Golf IV, manufactured in 2001, engine code AJM.
It often happens that the glow plug in the engine either doesn't turn on at all, or only turns on after a very long time (even when it's warm). Then, when starting, the engine immediately revs up to around 2,000-3,000 RPM, pulsating twice. After that, either the idle speed is normal, or it's around 1,100 RPM (and this isn't temperature-dependent).
Furthermore, it can also happen that when you are driving and stop at a traffic light, the idle speed suddenly increases to around 1100 RPM.
Unfortunately, there are no error codes stored in the system's memory.
Okay, so the question is: what's causing this?

Best regards,
Mathias

You have a VAG-COM device, right?
Take a look at the temperature of... (e.g., in MWB 1).
Kühlwasser an, ob da plausible Werte kommen. Otherwise,
replace the temperature sensor.

Best regards, Klaus.

Hello.

Today, I encountered the same problem again and checked the error memory once more. This time, it indicates "G62 temperature sensor."
I exchanged it today as well, and I hope that solves the problem.

Best regards,
Mathias