truck stalls after starting when its cold

[wells]

My 1988 F150 is hard start when it is cold, and you need to place your foot on the gas pedal to start it (not just the key). Sometimes it will start fine then stalls out when it is cold...once it is warmed up it is fine. It gets -30 here and my block heater is working. I have placed gas line antifreeze in the fuel tank and makes no difference. No codes on the dash. But sounds like a vacuum leak or excess air when the motor is running. Does anyone have any ideas what is causing

[carriedi]

a couple of things come to mind, MAP sensor, O2 sensor, coolant temp sensor, things that could make it run too lean when the engine is cold. weak spark, secondary ignition spark not strong enough with the engine being cold and putting an extra load on the system. If there are a lot of miles on the engine, timing chain could come into play here.

[wells]

what is a MAP sensor?

[carriedi]

sensor that measures the intake vacuum pressure.

What engine do you have in your truck?

[wells]

1998 F150 5.4 L i don't think i have a MAP sensor on it..i have already change the MAF sensor on it.

[carriedi]

ok, yes, you are correct. No map sensor. your first post said 1988 so I was basing my answer on an "88 f150.

Idle air control could be sticking so it won't keep up with the idle demands. Make sure the O2 sensor is reading correctly. There is also a possibility of a spark plug or coil the may be acting up that will affect you idle cold and the IAC not picking up the idle fast enough to keep it running with a miss. but the miss will go away when the engine warms up. You might also check for a vacuum leak into the system while the engine is cold.

[wells]

i have pick a iac valve, pv valve, fuel &
filtre to change this weekend

[carriedi]

you might try cleaning the throttle body and disconnecting the battery for 10 minutes. then reconnect the battery and let it idle for w few minutes

replacing parts can get expensive, sometimes it's better to have the vehicle scanned to find out what it's doing. So, in your case you would take it to a shop and leave it overnight and have them scan it in the morning and see what the engine systems are doing. Then you might find out what part or parts that need attention. But, even then, sometimes the diagnostic tree will say try a known good part.