The closest thing I can compare it to is the sound you get if you shake your car keys. My first car (82 Accord 5 speed) did it but it was old by the time I got it. My 92 Integra 5 speed didn't start it until it had around 60k miles. But I think my CL as always done it. On all 3 cars, I notice the sound mostly if I was in too high a gear for the current speed and gave it some more gas.

 

Im not positive... but I think mine might make the same sound. I only hear it every now and again tho. Everytime I hear it, it reminds me of the sound my old V6 Ford Taurus used to make when I went WOT. Kinda like what washers might sound like if they were on a bolt that wasn't tight. A fast metal against metal rattling sound.

 

Yeah, that sounds like it. I wonder if its the valves.

 

Mine makes the same sound... It is your engine pinging or knocking... check the post I just posted about it and follow the link in the response...

 

That sucks. I've always run premium but I am in CA.