Pontiac Repair: 2002 pontiac grand prix, crank sensor, pontiac grand prix

Question
Todd i hope you can help me. About a week ago my 2002 pontiac grand prix 3.8 start to do something strange. Some times during the day the car just turned over and would not start. When i went back later it would start and would be ok for days. The other day it did it again so i got it towed to the garage before trying to start it. They told me they checked fuel pump, pressure and all was ok. They did a scan while it was not working and showed nothing. They checked for spark and said there was none. They ended up changing a module under the coil pack ?? I think they said?? Well it's still doing the same thing again after working fine a few days. They scanned it today while it was working and no codes came up ??? Someone told me it could be something with the anti theft or my key to start the car could have a bad chip ???? Any suggestions ???

Answer
Hi Tony:

well it can be a lot of things. It has to be caught wen it will not start to see what is missing, Fuel pressure or sprak. it could be a theft system issue, when it will not start does the security lamp come on and start flashing? If so then I would look at a security system issue first. do you have a second key for this car? next time it will not start try the second key that is if the lamp is flashing etc.. If not then it's a fuel delivery issue or a spark issue.. These cars are not really noted for module problems. More crank sensor problems then anything else. The key here is to get it to act up and then logically eliminated the possable cause instead of guessing at parts. If I was guessing here I would say crank sensor or fuel pump if it's not a theft system issue.. If it does wind up being a fuel pump do your self a favor and get the fuel filter changed as well or you will do in a brand new pump as well from a plugged filter. good luck :)