Learn Finnish: Käynnistyykö moottori heti? - Does the engine start up immediately?

The base verb is käynnistää, which means to start something (like a person starting a car). By replacing the ending with the -tyä suffix, it becomes the automative verb käynnistyä, which means to start up on its own. The focus shifts from the person doing the action to the engine itself.

If I wanted to ask someone 'Do you start the engine immediately?', would I use the same verb?

No, you would use the transitive base verb käynnistää, because there is an active subject (you) doing the action to an object (the engine). You would say Käynnistätkö moottorin heti? In our example sentence, the engine is starting itself, so we need the automative form käynnistyä.

Why is the question clitic -kö used here instead of -ko?

This is a quick reminder about vowel harmony. The root word käynnistyä contains the front vowels ä and y. Because of this, any suffixes attached to it must also use front vowels, so the correct clitic is -kö.

Why is moottori in the basic nominative case instead of the partitive or genitive?

Because käynnistyä is an automative (intransitive) verb, it does not take an object. Here, moottori is actually the subject of the sentence since it is the thing doing the starting. Subjects of these verbs are in the basic nominative case when they refer to a single, complete entity.