you have a vac. leake or the oneway check valve is not working.....
Check for a stuck open thermostat, check for an always on radiator fan, control valve stuck partially open or a clogged heater core.
If the egr valve was stuck open, the engine wouldn't idle. If the egr valve was stuck closed you may hear excessive pinging (spark knock) and in most vehicles, the check engine light would illuminate.
It is just stuck,
Does the fan work? if not, check fuses. if does work, check coolant level first. Next, check heater valve in engine compartment, on fire wall, has ~ 1 inch hoses connected between the engine and to the heater core inside the passenger side. Have someone turn temperature knob inside car and observe cable on Heater Valve is moving. (Can be simple as the screw on top of heater valve loose or cable maybe stuck). Heater valve can be stuck closed. Check hose gets hot between valve and heater core.
You dont , it is controlled by the ECU , the is an "Idle Speed Control Valve" Which is located under the throttle body. should check it to see if the valve inside of it is stuck .
The valve has failed.The valve has failed.
stuck valve in valve body? solenoid valve faulty if it has one?
To open a stuck foot valve, first, ensure that the pump is turned off and the system is depressurized for safety. You can try to dislodge the valve gently by tapping it with a rubber mallet or using a wrench to apply light torque. If that doesn’t work, consider removing the valve and cleaning it thoroughly to remove any debris or corrosion. Reinstall the valve and check for proper function before resuming operation.
When you shake the PCV valve it should rattle. If it does not rattle then it is probably stuck and should be replaced.
If carb, the float valve is stuck open. Take air horn off carb and check.
Change the brake hoses, they get hard inside and won't release pressure, kind of like a check valve.