How to fix engine idle problems in your car | Elentra 2013

How to fix engine idle problem in this 2013 hyundai elentra car which has starting problem also. Sometimes it requires accelerator pedal to start. Recently it has been idling irregularly with a bit of engine vibration. The cause was not very clear. Can you help me out?
It took it to a mechanic and he replaced timing chain. Around two months since the problem was rectified it is working fine now.