96 Running issue

My son has a 96 Grand Am with a 4cyl twin cam.

Problem,
He was driving to work and lost all power and the car would just sputter. Every time he tried to start it, it sputtered and shutoff. It would not idle or anything. I went to tow it home the next day and it drove up on the trailer with no problem. When I got it home and started to drive it off the trailer it would not stay running for anything. It sputtered and shutoff. I replaced the spark plugs and boots, the fuel filter, and cleaned the air filter (APC filter) and it would run pretty good. It idled for about 15 minutes. I shut it off and started it a couple of times. When I started to test drive it, I shut it off and started it up again and all it would do was sputter and shut off. I have not tried to run any OBD codes, have to keep it running long enough to get to Advance Auto to run the codes. What else could the issue be? Camshaft sensor, Crankshaft sensor, EGR? Guess till I run the codes I could replace everything and still not find my issue huh?

Okay, since I couldn't get the car to Advance to use their code reader I used anouther. The codes I got were,,,

P0355 Crank position Sensor
and
P0420 Catalyst System Efficiency Below Threshold (Bank 1)

I changed the Crankshaft Sensor and both codes went away. Problem is the car still sputters and shuts off. Should I go ahead and change the O2 sensor in bank 1, or are there any ideas out there?

I would measure the fuel pressure, it sound like that may be your issue, or maybe fuel pressure regulator or even a clog fuel filter. Also when was the last time the car had a tune up and wires were replaced.

code p0420 is usually a converter failure code you need to pull the pre converter o2 sensor and put a back pressure gauge in there and if you got anything over 1 psi your converter is plugged and needs replaced

when cranking do you have spark? if no then the problem is in CKP sensor wiring. Most likely shorted or open wire since wires usually run against hot engine parts.

when cranking do you have spark? if no then the problem is in CKP sensor wiring. Most likely shorted or open wire since wires usually run against hot engine parts.

I do get spark because the car will actually start, it just sputters and kind of backfires. Originally I thought the catalitic Converter was clogged (have seen what that will do before) but I get alot of exhaust blow so I dicarded that idea.