Car expert
I just test drive a toyota camry 2003, I notice the rattle noice while accelating. I have a 2002 camry, it is really quiet, the seller told me that is because the 2003 camry has a timing chain instead of timig belt, I don't know anything about car, but I think something is wrong with it, could you please give me some information about it?
It is a big problem or not?

Thank you so much.

That could be spark knock! I'm also finding on 4 cyl models, the baffle inside the valve cover bent down and rubbing on the timing chain. This is from quick lube chains that insert the oil dispenser in there and bend it!
Pull off the oil cap, look in the hole, and there should be a baffle 7mm in the hole. NOT BENT DOWN. If all is well there, then go find some 89 octane gas and give it another run.
If the engine has a flutter noise when just starting, (try this with foot firmly on the brake) then that noise is the serpentine belt tensioner getting weak.
Last thing, there is a TSB on the intake manifold. They're made of plastic, and form a crack. This allows pulsating air to make rappid rattle type noise.
BTW, starting 2002, all 4 cyl models have a chain. All V6's still have the belt. All '07's are chain (V6 or 4)

Thank you for your information.
Today, the mechanic checked that and told me that it is air intake manifold problem, the price is around $600 , too expensive, but he told me I can let it be. If I want to fix it by myself, what I can do to fix it. Thank you again .