i have a 97 Mercury Grand Marquis and the engine and it lock up. So i went to the junk yard and found a engine where the insurance co. had junk the car cause the air bags had came out but on the windshield they had put on the car starts. i put the motor in the car and hooked up everything up. So now when i crank the car up it starts but cut off immediately. and i hear air leaking and then it stop leaking i think it maybe the bypass air valve and idle speed,or tell me some were to start looking at . ty for the help