around 2K rpms or less, my engine makes a kind of shuderring noise. I've popped the hood and revved the engine using the throttle lever, when I rev it to say 5K rpms and let them drop, I've witnessed that the valve cover makes a "nuhnanah" type noise from underneath it. It kinda sounds like a lawnmower on steroids!

 

Well, the rod knock would get louder as the rpm and load on the engine increased. From what you are explaining, this noise is when the motor is decreasing in rpm, right?

 

Yes! i dunno...i think it might be the auto tensioner! Preludes have had lots of trouble with this in the past. I think i might have to take it to Honda and see what they say.

 

Yes they did have problems with the auto timing belt tensioner. I am not sure what pes of noises are associated with it though.