I noticed thet you selected stalling as your problem. The emission code will not cause a car to stall. I think you need to clean the Mass Air Flow sensor and run a cleaner through the air intake.
The 2001 Mercury Cougar does not contain Freon. Freon was banned in 1996. I suggest you take this vehicle to someone who has the knowledge, tools, and skill, to repair the A/C system.
The positive crankcase ventilation valve on a 2002 Mercury Cougar is located on top of the engine; in the valve cover. It removes harmful fumes from the engine.
The evaporator emission system control valve on the 1996 Mercury Cougar is located on the left side of the car. It is in the passenger side headlight area.
Usually on the pass side valve cover
bleeder valve on cooling system
In the valley under the upper intake.
on the back right side connected to the intake manifold close to the firewall
The canister vent valve is located near the fuel tank. The canister purge valve is located on the engine.
Back left,tucked at top and wedged up to the firewall.
valve guides or seals are worn
where is the canister purge valve located on a 03 chevy venture
HeyJolly==It is by the receiver dryer which is that big shinny can looking thing by the evaporator. GoodluckJoe