Hi,Bit of an open ended question I think and depend on a few factors like..
Environmental conditions [where you live]
Condition of Air filter [first one to check ]
Petrol or diesel engine..
Phil, thank you for the detailed answer! I will come back when doing the throttle body cleaning.Ok so you edited the post.. Greece is a big country.. do you do mostly city driving.. environmentally dirty conditions.. car with 125Kon the clock and never been touched I would say to you.. remove the induction tube to the throttle body and you will be able to see the ICV [throttle body flap ] I would imagine at the mileage you have given it will be quite dirty.. the main problem here is you can quite easily clean the front of the butterfly flap with throttle body cleaner but it can be difficult to clean the back .. lifting a motorised throttle body flap manually can itself cause problems like lost throttle position due to the internals of the motorised unit.. removing the throttle body from the inlet manifold would make it possible for you to access the back of the plate but again you have to be careful.. if yours is like mine it has 2 possibly 3 hoses carrying water to the throttle body .. these would have to be blocked off with appropriate sized bolts to stop coolant flowing out. if I were doing it [have done it on a Suzuki Swift ] try and leave the motorised unit electrical connection to the body connected.. it will give you less room to work on it but disconnecting it can also cause you problems and a throttle body relearn might be needed if its disconnected.. always fit a new gasket back in place when you remove a throttle body from a manifold.. if not air leaks can happen.. you will find lots of info on you tube on how to go about cleaning an ICV on a throttle body.. on the injectors I would just run a decent injector cleaner through the system first and see how that goes..
Take your time and with a little luck you should be Ok.. it looks a fiddly job but doable with a little care.. if you take it off the T/B .. remember always fit a new gasket back in place of the old.. and make sure both mating surfaces [ body and manifold ] are clear of old gasket..Phil, thank you for the detailed answer! I will come back when doing the throttle body cleaning.