Nissan Repair: 1993 Altima wont start, fuel pressure gauge, throttle position sensor

Question
I have a 1993 Nissan Altima GXE 5 speed with approximately 88,000 miles.  Occasionally it won't start or won't stay running once started.  This problem seems worse when it's above 60 degrees outside and when the engine is hot, and doesn't happen if I have a full tank of gas.  I took it to the dealership last summer and before taking it I filled the gas tank on the premise that they may have to let it run to find the problem.  The problem didn't occur.  If I unscrew the gas cap once it fails to start it will have problems starting that time, but then seems to make it through the rest of the tank without problems.

From reading other answers on this site I suspect it might be a problem with the fuel pump, fuel filter, or throttle position sensor, but I'm not sure.  Any suggestions.

Answer
Steve,

I would be checking the fuel pressure.  And, the regulator, pump and relay for starters.  Get a Haynes manual for $20 bucks and a fuel pressure gauge and you can get the information on what the pressure should be.  Basically, if the car has the pressure then you need to be looking at the idle air control valve, throttle position switch and cleaning the throttle body to make sure the engine is receiving and controlling the amount of air entering the intake at idle.