Personally the timing chain and belt go hand in hand. You will know!! I recommend them be replaced together at the same time - others may differ with me. You'll know - the car will not run... it will idle. You should get this done before that happens. A trusted mechanic and the mileage of your car will be able to tell you right away. I say that...........well a trusted mechanic can! For me....it's protocal with "certain cars" and mileage...it comes recommended. Have it checked out by someone (mechanic) you know and trust.