Banging inside of the air intake manifold?

[nmu1974]

This isn't really a Ford truck question but maybe someone can help me out and shed some light on my (my son's) problem. He inherited his grandmother's 1995 Mercury Sable 3.8 V-6 with only 80,000 miles. Yesterday a severe banging noise seemed to be coming from within the air intake manifold. It is very loud and it feels like someone is on the inside hitting it with a hammer. Whatever it is seems not to have an affect on performance. What is inside that could possible be causing this noise? Does this sound terminal? Any thoughts on cost of repair? (He just got his drivers license 2 weeks ago and I hope that this isn't too hard of an introduction into the wonderful world of auto ownership). Is it something he (I) could attempt to repair in his (my) garage? Thanks in advance, even though it's not a truck.

 

[tonkadoctor]

Check for mice in the air filter and associated ducting, especially if it hasn't been driven in a while.

 

[nmu1974]

Check for mice in the air filter and associated ducting, especially if it hasn't been driven in a while.

Thanks for the reply. I thought of that and took a look, couldn't see any debris. Besides, it really sounds like something is actually hammering on the manifold from the inside. I know mice couldn't do that - it's that no thumb thing on those little critters.

 

[mr_josh]

Sounds like it's backfiring in to the intake... I don't want to know why. Bad intake valve? That's all I can come up with.