Hello,
I just picked up a 2000 Blazer with a 4.3 Vortec and 4WD.
I'm getting a very weird noise coming from the intake area.
It sounds somewhat like sucking through a straw when your drink is empty. At first I thought it was coming from the front speakers but after opening the hood i realized its coming from the area of the intake sort of under the intake hose.
It happens after the truck warms up and anytime I'm not on the gas. If I rev up the engine the noise goes away, but as soon as I let go of the gas, the noise starts and gets very loud.
Can it be a valve of some kind leaking air or something?
Any help would be appreciated.
Thanks.

 

take the air intake off of the throttle body and spray starting fluid on the intake manifold and the various items hooked to the manifold. when the engine revs up. you found your intake leak. just don't spray it into the throttle body or near the distributor.
and spray it sparingly so you can pinpoint the problem quickly