1999 fire bird wont start

Mass air flow sensor maybe drity or going bad . Ever had it replaced ? Have you replaced the air filter lately ? Video's on youtube showing how to clean mass air flow sensor , you would have to buy a can of mass air flow sensor cleaner . Also while your at it clean the throttle plate , again there are videos on youtube . How did you check fuel pump ? To do it right you would need to hook up a pressure gauge . Also check flow .Videos on youtube .Has the check engine light come on ? Also you mite try some fuel injector cleaner and or dry gas for moisture in the fuel !

Mass air flow , crank sensor . I wouldn't discount anything . Having a scan tool that can view engine sensor data would be a great help too , testing fuel pressure and flow and back pressure test the exhaust .
058 Engine Hard to Start or No Start Lean Fuel Condition
055 Engine Hard to Start or No Start Scan Data for EGR
057 Engine Hard to Start or No Start Ignition Module Test
007 Catalytic Converter Testing

There is a switch in the airflow meter that keeps the fuel pump relay closed as long as there is airflow. With the meter unplugged, the pump should not run except when the key is turned to start. It would seem to me that you have a wiring issue. Try jumping the fuel pump relay so the pump runs whenever the key is on. (Remove the relay and jump the pump wire to the accessory wire--see top left diagram.) This defeats the safety feature but will keep the pump running.

Clean throttle body

Could be a couple of things. First check the fuel pressure because it could be a clogged fuel filter or a bad fuel pump. Also could be throttle position sensor or mass air flow sensor.

i would agree with your diagnosis. i had a similar problem with a crown victoria. disconnecting the maf sensor made it run better. i replaed the sensor and have had no problem since

your computer is reporting bank 1 and 2 too lean, usually caused by the mass air flow (MAF) sensor, you can usually clean this sensor and reset the light. Clean it with electric cleaner or brake cleaner, make sure it is dry before reinstalling, also take care not to damage it. Hope this helps, let me know

If air filter is the round type then remove it and see it the black cone on the end of it didn't come loose and **** up inside the filter so it is blocking air to the Mass Air Flow Sensor. If that is ok then clean the MAF sensor bulb with a good electrical cleaner then let it air dry before hooking back up and see if this corrects it.

unplug your mass mass air flow sensor an see what happens when running and let me know

If you unplug the MAF sensor it should run using the default mapping. I'm having the same problem, but I want to figure out why it won't run with the sensor connected.