yes it runs off vaccum from the engine, it only works when the car is at cruising speed, not at idle or flat foot.
If the egr valve is stuck OPEN - the Engine will run Very rough & idle bad - or not idle @ all-if the egr valve is starting 2 stick IT WILL TURN ON THE CHECK engine light-Sometimes U can take the valve off & clean them with a GOOD carb cleaner.
Yes, it can cause low/unstable idle or die off at idle.
You cannot simply turn an EGR valve off. You can clean it, replace it, or remove it, but you cannot turn it off.
Cruising down the highway, off idle.
The A/C idle compensator solenoid is not functioning. This should be located next to the carb.
Leave it idle.
Could be several reasons such as a large vacuum leak, a faulty EGR (Exhaust Gas Reclaimer) valve, a faulty MAF (Mass Air Flow) sensor,
Yes, it could.
I would look into a stuck open, or jammed Egr Valve.
Cheaper to turn it off.
yes
Idle jet in the carb is clogged.