Please, need help guys!!!!

I have 97 Century, a week ago my engine was replaced. The computer remained old, now I have a "service engine soon", scanner says the crankshaft position sensor, mechanic swears that it's not that since he switched it from the old engine, he says it's a glitch in the computer, however, the light comes along with the problem of starting the car, engine shuts down while running at the light or when I hit the gas pedal to the floor it responds in shaking, sounds like something is shooting out. Mechaninc also said, he changed the module, but suggested to go to the dealer and get the computer re-programmed. Also is it taking a long time to change the crankshaft sensor? Can the sensor mulfunctioning cause those problems? Thank you very much, I'll appreciate all replies.

First of all the sensor could have been bad especially from the old engine. He should have put a new one on a new engine and when he did he should have done a quick case learn procedure so that the ECM would have recognized the new sensor. Takes a couple of hours to change depending on the engine.

I would trust the computer on this one since the symptoms you describe are those most commonly seen with a CPS problem. Whether the computer is new or the old one as long as you aren't experiencing major computer issues it should be fine. New CPS should cure the problem. Good Luck!

Thank you very much for your answer, it's just like I thought, I knew he didn't want to change it because he didn't have time to since, I was not paying him extended warranty did, basically he lied to me, probably didn't even bother to do anything, I could have gone to the dealer here in Philadelphia and pay 97 bucks only to figure out what was the problem, thank you again, Arthur