I have a 2000 Acura Rl with a ton of miles on it. Some lifter noise is to be expected. I have tried using different weights of oil and oil stabilizers. All with the hopes to eliminate the rattle i hear. Generally is a constant thing at idle. It could be hot or cold doesn't matter. When i give it some RPM it tends to quiet down. Anyone else ever had this problem? If so what was it? Id like to confirm what it could be before start tearing things apart. the car just runs too well haha.

 

Is it a tick, tick and tick sound at idle? My car used to make that sound in cold temp. but now is completely gone. I really don't what happen; I think it just went away by itself.
BTW, I'm currently running 20w-50 for summer time. I think I'm going to switch back to 10w-40 and add Lucas engine treatment.

 

These engines have hydraulic tappets that sometimes stick. When I first installed the motor in my RL I had one that was ticking, I eventually tried some Marvel Mystery Oil which seemed to do the trick. Try something like that or Seafoam before you start tearing the top end apart.
Also is it possible you're hearing the fuel injectors? Just a thought but best to rule out anything that makes a ticking noise.

 

The tick happens at idle. I am running 5w30 weight oil and about a half of pint of seafoam per oil change. I wonder if running 10w40 and lucas will help pressurize the stuck hydraulic tappet. I'll let you guys know what i come up with. Oil service is due soon!