Hopefully someone can help. At idle, wheather in park or not, there is an uneven sounding rattle coming from the engine compartment. It sounds like something is loose. Also, it's more of a low frequency sound, not like piston slap or a valve.

 

it could be a million things!

pcv valve
battery coming loose
loose fan shroud
does it still make the noise with the hood up?
some people on here have reported alternators and airconditioner compressors coming loose
do you have any under the hood mods?

get a real long screwdriver and hold the handle to your ear and start touching the blade end to suspect rattle makers under the hood. BE VERY CAREFULL to stay away from moving parts and electric conections!!! it works just like a stethoscope.

good luck!

 

has rattled since new...borrow one of those sound stethascopes and I'll bet thats what it is...I didnt have one but to satisfy myself I took the belt off and started it for a minute and the noise was'nt there,then I put it back on and it returned ...right around that alternator

 

Thanks guys, but I still don't know what it is. It does it with the hood up as well as down. It seems to be coming from deep iside the engine (below the intake manifold) near the firewall. It sounds almost like a small drum is being played.

 

try the old tube method. With the engine running, take some kind of tube (I use an extension tube from my home's hoover vacuum) and liten through it, pointing at different parts of th engine till the culprit sound emerges...worth a shot.

 

It could also be a heat shield or a Cat converter. I had a simular problem with mine. After repeated visits to the service department, it was my driver's side Cat making the noise. It was replaced and not a problem since....(knock on wood)