My 2004 5.4L FX4 F150 is stalling out when I get to a stop light/sign, it also does when I go from park to reverse or reverse to drive. It idles very low and will sometimes feel like it is going to stall but then revs up to 1000 or but the needle will jump back and forth from 1500 to less than 1000. Please any suggestions are greatly appreciated.

How long since a tune-up? Have you checked the timing? How many miles on engine? How is your cylinder compression?
There isn't much load on engine in park or neutral. When you put it in gear, there is a load on the engine. With carbed engine 6--8 psi fuel pressure. Crub idle in drive, 575 rpms. With a high mileage engine, that idle speed may not work. Is there an idle screw on the carb, where you can up the idle to keep it from stalling, in gear? Of course if you do that, when you put it in park or neutral the idle is going to go high, I know it's a pain. If your engine is in poor shape, your probably going to have a tough time, getting it to run correctly. Just my opinion.

Any DTC'S - diagnostic trouble codes ? I would have the vehicle checked , could point you in the right direction an shorten your diagnostics . Your vehicle has a number of control modules , PCM , SJB , air bag , antilock brakes , instrument cluster , They all share information on a serial data communication bus . You could have one of any number of problems that could cause a stall condition . A shorted transmission range sensor , crankshaft position sensor . You could have a bad ground somewhere . Unless your an automotive electrical an electronics wizzard , I suggest you take it to a qualified repair shop .

Is the check engine light on ?
Have you checked the computer for trouble codes ?
You could have one bad spark plug even with only 30k on it.
Problem could also be a dirty injector.

my 2002 ford f150 4.2 would not hold idle so we changed the fuel pump and fuel filter and relay now the truck starts holds idle runs good at low rpm but when i stomp it it runs then stalls and picks up again.

Do you have a check engine light coming on?

Check there are no air leaks on the air intake system. - check all the clamps/hoses etc that may have been removed to replace airflow sensor.

Hi!
Check the park light switch may be the contacts are worned or need cleaning.

low idle speed...or the need of a tune-up

sounds like the torque converter lock up might not be disengaging. You might also want to check for engine vacuum leaks. Does engine idle smoothly when in park or nuetral ? if the idle is good I would suspect torque converter problem.