Fuel timing

Hi this might sound silly but to adjust the timing do u need to lock the engine with the pins first before u can ADVANCE or RETARD it.

This is on a 1.9 pd BXE.

Am only asking because I've got a rough idle everthing has been been checked and it's all fine

( injectors, wireing loom , sensors , you name it it's been done last thing to check is timing that's why am asking about the pins or can a just crack the 3 bolts slightly and move the sprocket slightly either way to get rid of this rough idle HOPEFULLY.

Cheers Graeme