Sup,

I have a 97 F-150 4.6 4x4.

Seems like, after I put a cold air induction on, this problem started, but not sure.

I will be driving around, and come to a light. When my RPM's drop to about 1000 sometimes my truck will let out a LOUD constant sound that resembles a horn (or possibly a wounded cat like I have read here). It goes away if I rev the engine, or start moving. It's doing it more and more (which could be related to the cold here), and when I listen to it, it sounds like it is coming directly from the engine thru the cold air induction.

Any ideas?

Thanks
Robert

 

the idle air control valve is resonating.replace it and the noise should be gone.

 

ford air valves suck dont they... im on my second one in 40K miles