Does anyone know what would cause a 2006 ford ranger with the 4.0 engine to stall, randomly, when breaking or alowing down? I have taken it to my mechanic twice and neither time did it act up while he had it. He kept it several days at a time and still didnt happen.

Could be a couple things causing the brake stall. If no check engine light is on. I would start with. Running sea foam through the vacuum lines to your throttle body. Those vacuum lines do assist in power brakes. It's probably the answer. It will clean it out. It will smoke really bad for about 5 miles. But should solve the issue. A partially plugged catalytic converter will do the same. If that is the issue you will have to clean it or change it. If you clean it. The easiest method I have found is to. Pull both O2 sensors spray two cans of sea foam deep creep into your number 1 O2 sensor hole. Spray the first can in let it sit for 15 minutes. Then start truck and spray the second in. Leave both O2 sensor's out. Drive for a about 10 miles. It will smoke really bad. Once your home again. Shut truck off take positive cable off of battery. Let the exhaust cool down. When exhaust is cool put O2 sensor back in. Put your positive cable back on battery. You just cleaned cat and reset your computer. The last thing it could be is your e vap. That's the cannister looking thing back by your spare tire. It's probably not that but a bad e vap could cause. I would start at the vacuum lines going to throttle body. It the easiest most likely.

Agree with everything guru is saying. Throttle body clean would be my first task, then if there are no error codes check your wiring harness and make sure you have proper air flow with air filter/intake. I know it's step one but I have made the mistake before of replacing sensors and wasting time when I should have just checked for the main things that make a car run... Spark, oxygen, and fuel. If it's sputtering out I'd say start with oxygen issue and then head to the fuel step next and then plugs and wires or the wiring harness itself if no error codes. Either way no codes to me means no connection to get the codes or not enough air getting in. I'd undo the air intake and just run it at idle and see what happens. First thought is not enough oxygen getting through. If you hear a whistling noise or heavy vacuum sound coming from air intake that's the issue