A1 1.6tdi idle at 1600rpm?

Hello guys

first time I ever come across this weird issue, car on cold start will start up normal and idle at around 800rpm. As long as I am gone for a drive it no longer idles at 7-800rpm it will now idle at 1600rpm. There are no fault codes in the system and I initially thought it may have something to do with car being stuck in DPF regen mode however I know if it was stuck in Dpf regen mode the main fan would always be on but the fan doesn’t come on so it can’t be that.

anything else worth checking? I was thinkin possibly a sticking throttle body?

The throttle flap has nothing to do with fueling, the engine speed is controlled by injection volume.

Check air temp sensors. The theory being if it thinks your freezing it may add rpms to compensate