Q: Engine cuts out when breaking

Check the brake booster for any vacuum leaks. The brake booster check valve could be split, the brake booster supply vacuum hose could be loose or split, or the brake booster diaphragm could have a slight tear or a pin hole. A vacuum leak on the engine’s brake system will cause the engine to stall out during braking. If the brake vacuum system is good and there is no leaks, then the Idle Air Control valve is sticking causing the idle to not return properly and making the engine stall out. Try applying the parking brake slowly and see if the engine stalls out. If the engine does not stall out, then it is vacuum related. If the engine does try to stall out, then it is the Idle Air Control Valve issue. If you need further assistance with your engine stalling when pushing on the brakes, then seek out a professional, such as one from Your Mechanic, to help you.