AJM starting problem

Hello,

I'm having a problem with my Golf IV, built in 2001, engine MKB AJM.
It often happens that the heating element either doesn't light up at all or only lights up after a very long time (even when the engine is warm), after which the engine immediately starts and revs up to around 2-3,000 rpm. Then it runs in pulses for 2 times, after which the idle speed is either normal or around 1100 rpm (regardless of temperature).
Furthermore, it can also happen that when I'm driving and stop at a traffic light, the idle speed suddenly returns to around 1100 rpm.
Unfortunately, there are no error codes stored in the computer.

So, what could be the cause?

Regards, Mathias

[Translating...]

Du hast doch VAG-COM, oder ?
Schau Dir mal (z.B. im MWB 1) die Temperatur vom
Kühlwasser an, ob da plausible Werte kommen. Ansonsten
den Temperaturgeber tauschen.

Grüße Klaus

[Translating...]

Hallo

Habe als heute erneut das Problem war nochmals in den Fehlerspeicher geschaut da stand jetzt G62 Temperaturfühler .....
Hab den dann auch gleich heute getauscht ich hoffe mal dass es jetzt weg ist.

Gruß Mathias