l was told that all fuel injection engines, regardless of age,make that sound.Is this a fact?

Valve train. Probably have a valve or 2 not set at the propper lash.

It is called 'pinking.' You're using the wrong fuel or your timing is out.

It could be several things. Your valve train could be out of adjustment. Periodic valve adjustments r required on vehicles with solid lifters. Unless u r good with mechanical things & have the right tools, u should leave this to a qualified mechanic. It is not difficult but if not done right can cause serious damage.

Modern fuel injectors r very quiet & l doubt that is the problem.

One other possibility is oil level. If ur oil is too low, the pickup in ur oil pan will cavitate & this will cause the valves to get very noisy.

If none of these things fixes it, l would bring it to a good mechanic. It is difficult to properly troubleshoot automotive noises without being there.

is the sound on all the time or when the the key is on? mine does the same thing. the click noise is so you know it is working

Toyota Rav4. could be the pistons.