Help with 98 Cavalier

[slace22]

First thing, i had my car put on a computer and had some things fixed but i still need a new ignition coil, fuel injector , and oxygen sensor, my question is would any of these things cause this problem i am having.
The problem... When the car reaches a certain temp. it shuts off , it is not over heating.
On a cold day the car will run forever because the temp gauge doesnt reach that certain temp, on a hot day it will rise faster and shut off , and like i said the car itself is not overheating when it shuts off but it seems to think it is.
Every time the temp gauge gets to the 1/4 mark it shuts down.
Could the ignition coil or oxygen sensor really be causing this problem?
Like i said i had it on a computer and those are the problems that came up.
Thanks for any help.
HR

[J-Ri]

oxygen sensor would not cause that.
fuel injectors would probably not cause it, unless there's a heat sensitive short in one that is causing the PCM to fail (very unlikely)
a bad coil would not cause it, because there are two coils, and both would have to fail simultaneously for it to just shut off. if it was just one bad coil, it wouldn't shut off, it would just run like crap.
my guess (keep in mind this is without looking at it), is the ignition module.