Drone sound from engine only at 20-40% throttle

[youdontwannaknow]

The MDX has started emitting a deep drone type of sound but only at certain times. After having ruled out whether its occurring at certain speeds or in a certain gear I have concluded that its happening at specific throttle positions only regardless of what speed or gear the vehicle is in.
It happens only when the throttle is in about 20-40% range. Its not loud but noticeable enough to be annoying (although I am more sensitive to unwanted car noises).
My first guess would have been some kind of resonance in the air inlet or maybe exhaust sections but cant imagine why only now and what could be the possible cause ?

 

[HerrStig]

Hoses and intake tubes are allways suspect, but my bet is an exhause leak. Does it make the same noise in neutral as it does under load at that RPM?

 

[youdontwannaknow]

only under load.

 

[hypervish]

Check exhaust gaskets for leaks.

 

[HerrStig]

My bet is exhaust related.

 

[youdontwannaknow]

ok I will check but just for my understanding - if its a leak in the exhaust, or the intake for the matter of fact, why wouldn't it sound like that all the time ? Why only at specific time only ? I don't think the engine sounds any different now than it used to at idle or when revving it up in 'P'ark either.

 

[asand1]

My maxima does something like this. A noise can be heard that originates in the fuel pressure regulator, is amplified in the fuel filter, and finally resonates audibly from the firewall.

Many members of maxima.org have come together to troubleshoot and solve this issue.

Check all the hoses and hardlines attached to the firewall, as it will amplify smaller noises.