I have spent days trying to fix a problem with my 300 ZX. When I start it in the morning it takes several cranks before it finally fires. I turn the ignition key on and just let the fuel pump engage and then turn the key back off and try to fire it. After several attempts the car finally fires. As I turn the key off it attempts to fire. I have replaced the ignition switch; wiring to the coil; plugs and wires; alternator; fuel filter; fuel sensor and gas tank. After it finally fires I drive it and it stalls a couple of times (even if I let it run until the motor is warm it does this) on my way to work. After I drive it for 3-5 minutes at speeds greater than 35 mph it runs great. Sometimes after work (the car has been sitting for 8-10 hours) the car starts fine but then stalls a couple of times until after I drive it again for 3-5 minutes. Sometimes it starts okay and runs fine without stalling. This has been going on for almost a year. I did take it to two mechanics and they cannot figure it out either. Any suggestion would be appreciated.