I've noticed recently my cars being a bit funny with its tick over.

It seems to be entirely random at what rpm it ticks over at.
I.e one time i stop its 900rpm, another itll be about 600 rpm.. and so on.

Its not hunting as it holds these revs quite steadily and it seems to make no difference if you blip the throttle, it still goes back to whatever revs it was before, it just next time i drive off and stop it'll be idling at a different rpm!?

Is this normal?

 

The 900 figure seems right but 600 is low but it should be stable.

If you have aircon it should increase the rpm when on.

 

Mine idles around 800, sometimes 750. It's pretty consistent though, only changes depending on whether the car is cold (over 1000RPM when first started) but you can drive around when warm and every time you stop it settles around 750-800.