Well it obviously regulates vacuum. But how? Mine was open to air. Nothing attached. Have now fitted a clear plastic tube with a plug. Just to test. Is that wrong? Should the vrv be open to air (where my shiny plastic hose is fitted) or what should be in its place? I have seen the vrv being plugged on another engine but can't find any info in the Chilton manual.
Ofc, that was stupid of me. Its a Buick LeSabre Estate Wagon -87 with an olds 307. Did do a test run with the vrv plugged as on the picture. The engine was running very well at 55 mph, but when slowing down to 25-30 it got horrible. My guess is that this valve should be open to air, or maybe there is something else missing that will control the vacuum.
I need to clean this engine bay, it looks terrible. But in my defense it is often run on a dirt road.
It is supposed to be open. Those valves will regulate the vacuum coming from one port to the other, usually to only allow vacuum above a certain threshold. These will often have a smoothing effect on the output - meaning the vacuum source can fluctuate but the output will not, like for your spark vacuum advance or diaphragms that are supposed to open and close at certain times like an EGR valve (model\application dependent). The other side is open to air to release the vacuum on the load side when the source falls below the threshold.
Thank you very much. I understand the concept and think as well it should be open. Its just looking a bit weird, the connection is having a design that does look like something should be connected to it.