93 escort lx wagon stops when braking

My escort runs good when driving between 20 and 50mph. However when I break at an stop light or while I'm waiting in line at the drive though in Mcdonald's or something the car will shut off. It starts right back up without any hesitation but whenever it's in park or idling the engine seems like it wants to shut down and often does. What could this be???

Got a vacuum leak or a bad Idle Air Control or a defective PCV valve. The PCV valve is located in the crankcase vent tube just below and to the left of the the plug wires going into the coil pack. Take it out and shake it. It should rattle. Also, you should be able to blow into it one way and not the other way. The Idle air control is just above the throttle body which is located at the left side of the intake system. It looks like a small motor no bigger than a spool of thread and has a connector with wires going into it. Take the 2-8mm screws loose and take the wire clip off and pull it. Clean the inside of the IAC with carb cleaner and then lubricate the 2 cavites with WD 40 or a light machine oil such as 3 in 1 oil. Don't do or spray anything into the surface it is mounted on. You should be able to reuse the gasket if it doesn't have any sealer on it.
As far as the vacuum leak it sounds like a high pitched whistle noise. Check all the hoses coming off the intake plenum (manifold). One way to find the leak is to pinch the hoses with a pair of needle nose pliers while the engine is running. If it changes speed that is the hose that is leaking. Either at the source or further down the line. Check it out.
All the best. Dave