I am beyond 120 000 km (not miles, mind you) and was supposed to have spark plugs changed and get the valve adjustment done at 120 000 but last time I had the oil changed, it was before 120 000 km and only now having about 121 500 I realize at the next oil change the car will have run about 130 000, which is a lot more, so I am a bit worried about the spark plugs and valve adjustment. Anyway, this morning the engine went very jerky after the cold start. The revs kind of jumped up and down quickly, I think jerking is the right word, like the hand job... very quick movements... I drove away and it was ok after a while as the engine warmed up. I'll see tomorrow if it happens again. But this could be a problem with the spark plugs or valve alignment? May I damage something expensive if the change of spark plugs comes too late or if the valve alignment is too late? Thanks for advice. I suppose spark plugs are pretty cheap so I'll have them replaced to make sure the engine runs ok, but the alignment, I'd rather wait until next oil change, if it is OK.