Misfiring, now not starting

[Alpha One]

From bad to worst.

This morning the engine was running as yesterday, misfiring but running. I started the engine to check it again with my ScanTool. A few minutes later it stalled and didn't start again. I have the original Computer that went bad maybe 2 or 3 years ago. The engine worked rough with it but worked; I tryed it before yesterday and the engine started and run.

So, gessing that maybe the Computer went bad (I had boght it used) I replaced with the original I had from before, but the car didn't start either. So I am assuming that its not the Computer but I have no idea what to look for next.

I checked, again, the fuel pressure, for spark in the spark plugs, for disconected vacum hoses. Fuel pressure is about 42 psi, there is spark, and I didn't see signs of vacum leaks.

Trying to fix this non-start condition I replaced the Crankshuft Sensor and the Camshaft Sensor.
Nothing!

When it stalled there were no noises or anything else, it just stoped running.

Could it have anything to do with the scurity system?

[Smith1000]

This sounds like what I went through with an old 87 Oldsmobile I had. It kept misfiring and stumbling. I replaced the plug wires, plugs, etc. It would go, but not very good. Nothing I did seemed to improve it. I replaced the computer and the ignition module. It still didn't improve. I kept fiddling around with it for several days. Finally, I happened to be looking in the trunk for something and noticed I had a broken ground wire in the trunk. I pressed the wire to the frame and the engine smoothed out and ran great. It ran great for years after that. Might check or clean all of your ground wires under the hood. Make sure they are all connected and sanded clean. My 97 Lesabre has a bunch of them on both sides of the engine. Several connect near the computer. I am not sure if this will help, but it seems like you have replaced all of the major stuff. Maybe it is not getting a good ground. I think the ignition module has a ground wire that fastens near a bracket on the passenger side of the engine. Also, might ensure the battery cables are good and clean. The Olds I had would also run poorly when the valve cover leaked oil down around the plugs. It would short out or something.