If your vehicle is showing car dies when coming to a stop or idling at a red light, here are the most likely causes and the parts you'll need to fix each one.
Carbon buildup in the throttle body or a failing IAC valve prevents the engine from getting enough bypass air to maintain idle when you take your foot off the gas pedal.
A cracked hose or failing gasket allows unmetered air into the engine. This leans out the air-fuel mixture, making the engine stumble and stall when vacuum is highest at idle.
The MAF sensor measures air entering the engine. If it is dirty (often from over-oiled aftermarket air filters) or failing, it sends incorrect data to the computer, causing the engine to stall at low RPMs.
The EGR valve recirculates exhaust gases to reduce emissions. If carbon buildup causes it to stick open at idle, it chokes the engine with exhaust gas and causes a stall.
In automatic transmissions, the torque converter clutch locks for fuel efficiency at speed. If it fails to unlock when coming to a stop, it stalls the engine just like forgetting to press the clutch in a manual car.
A weak fuel pump or clogged filter may fail to maintain adequate fuel pressure when the engine drops to idle RPMs, starving the engine of fuel.