1999 pontiac - sunfire- will not run

sounds like a fuel delivery problem, have you had the OBD read ?the backfire could be a symptom of timing out or misfire so need to check a few things

There isn't one.

tune up,coils,wires.

fuel filter,fuel pump,water in gas,dirty injectors

I agree with Peter on this one. Sounds like low fuel pressure. First thing is to be sure that you have around 55-60 psi when you turn the key on and running should be around 55. If the pressure drops much below these no.'s the fuel pump may need to be changed. Don't forget to check and/or change the fuel filter also.

Change the fuel pump or make sure the fuel safety cut off switch didn't trip or look for a blown fuse. The fuel cut off is usually found in the trunk.

Dirty throttle body . Does it run good when you step on the gas pedal ? driving down the road . Don't guess , do fuel pressure testing . Videos on youtube showing how , fuel pressure tester under $30 most part stores .

If u replaced the fuel filter and you still have no fuel pressure to the fuel rail, your pump is bad.

Check your idle air control valve.

it sounds like the fuel pump needs to be replaced
the fuel pump is an electric motor the fuel in your tank keeps it cool but when you run the fuel dry the pump overheats and can seize