When our 91 b4c Camaro gets warm it won't run at all. We've tried changing the computer, but it does the same thing. Tried wiring the fan to a switch and turned it on before it got very warm (several times) and it still won't run. Any ideas?

 

Maybe a new coolant temp sensor? 2 wire sensor located in the intake by the thermostat.

 

good choice.
when the coolant temp sensor goes bad it shows negative degrees temp, something like -40f.
unhooking the sensor will show the same -40, it must be replaced to test unless you have a pc based scanner.
its only 35 dollars and they go bad VERY often.
make sure the parts counter doesn't give you the one for the gauge.

usually signs of this are stumble thru the entire rpm range, sometimes clearing at higher rpm, and massive power loss that gets worse as temps rise.
no restart when hot is also common.
often mis-diagnosed as ignition problems.

let us know if that's it