Valve's or pinging??
 

My 2000 accord 4cyl has been making what i thought to be raddling valves especially when cold. Now,honda sais I don't need to change my spark plugs for 100k because they're platinum tip plugs. I went ahead and did a valve adjustment yesterday while the car was cold and the valves were within specs but,i decided to tighten them to minimum specs. when I started it up the engine was quiet and smooth but,still made the raddling noise only after i reved it up. one reved and then i release the pedal,the idle falls,the jumps back up alittle(thats when i hear the noise) then it falls back to normal. I went ahead and replaced the plugs because they were shot and wires,cap and rotor. that seemed to take care of the problem somewhat but,it still makes the noise under acceleration(just not as loud). I'm thinking it could be something to do with the egr system but,I have no check engine light on and the car only has 57k miles. any suggestions???

does the noise sound like gravel slowly being dropped on your valve cover?

maybe,the car is alot more smooth and quiet after the tune up but,you can still hear this noise during acceleration. Its not an obvious valve tapping,it sounds like the valves are all raddling equily during acceleration or when the idle falls back down when sitting still. the valves are adjusted properly,I'm 100% sure. I'm wondering if the cat. convertor is clogged just enough to cause a slight backpressure if you will,on the engine or the exhaust gas is not recirculating through the engine properly.

I would say that it's normal. My 99 accord has done this since it was brand new. I even complained to the dealer about it a couple of times but I noticed every 6 gen 4 cyl does it, especially when cold.