Why would a car start but shuts off after it is put in gear?

There can be several things to happen this on A/T engines.

• Engine Idle Speed is low, below 750 Rpm +-50.
• Engine air lines leaking.
• ignition system problem, misfire on some of the cylinders, because of this engine does not run smoothly at idle. ( so engine rough idle)
• Engine mechanical condition.
• ECM is not increasing the engine speed.

Basically the engine need to tune up if mechanical condition is ok. if mechanical condition is not within limit then the engine need to do a top overhaul or a major.

It could also be the ignition switch...the car will start up fine..the key is turned to the start position but as soon as it pops back into the run position it turns off. It's an electrical problem and is very common. Stay away from puddles and auto-car washes. Shouldn't cost more than $250 for parts and labor.