help please

i have a 91 f150 with 5.0 truck will sometimes die when stopping for a red light and /or will sputter and cough on take off from a stop. it is also very hard to start will start after several short cranks and will act as if flooded at this time. will not attempt to start if cranking it in one long attempt. seems to be worse on rainy days or cooler days. i have changed the iac which seemed to help with the stalling problem but not a lot of help.

In my experience, I can tell you that a cracked or fallen off vacuum hose can cause any or all of those symptoms. When was your last tune up? Don't forget the air filter. It may be clogged causing rich mixture and rough idle.

to date i have changed the following iac valve, coolant temp sensor, distributor cap, rotor, fuel filter, plugs, wires, thermostat, checked all vacumn lines, clened throttle body. still have same problem no matter which tank i use. thanks for any more help i can get.

does it make a differance if engine is hot or cold?

not a lot of difference if it sits for more than 10 minutes or so

so it runs bad only at idle & on accel. from a stop?after you get going it runs ok??

the big problem is not starting you have to crank and crank and crank, especially after sitting several hours or overnight. if you turn it off it will start right back up every time. i can stop for 5 minutes or more and the no start problem will be there. when it does start it seems to act as if it is flooded. when you take off it will sputter for a couple of times unless you feather the pedal then it will pick up and go.

Hard to start cold. At this point the metal parts are slightly shrunken (thermal contraction) There is an air leak somewhere that closes itself up when engine is hot (thermal expansion) Look at all intake connections , manifold to head joints, leaking gaskets, maybe a crack in a casting. Have someone crank the engine while you listen for hissing air being sucked in.

have you taken a fuel pressure reading?after the trucks sits have someone crank engine
while you spray carb cleaner in the intake.see if this helps at all you maybe losing fuel prime

I have seen fuel pumps going bad do this exact same thing. especially starting hard. It can be the fuel pressure regulator also. Have the fuel pressure checked on the rail then at the filter and that will tell you if it is the pump or regulator or neithr one.