First go to the site that I listed below so you can learn how to pull codes from your computer.The check engine light doesn't always come on when codes are present.A few threads down the page,click the one for diy koeo/koer/cylinder balance test.It shows a description for the 87-93 Mustang,but your test connecters and electronics are identical to the Mustang.This needs to be your first step.It may tell you exactly which sensor(s) is faulty or it will lead you in the right direction for trouble shooting .I could list numerous sensors that can cause your problem but doing things this way will keep you from buying sensors you don't need.There are a few things I can tell you to check though which are free.Remove the vacuum hose from the fuel pressure regulator,check the regulator vacuum port and the inside of vacuum hose for the presence of fuel while the truck is running.If fuel is present,the regulator is bad.Remove the iac valve from the throttle body,disassemble it,BELOW

Start with cleaning the IAC valve and throttle body and plate, and then look into a tune up.

thank you guys i will try this!!

Can you be more specific please?

my ford f150 turns on but idles in and out. it will dim to the point of almost dying then come back to normal and repeating when i do get it warm it will die when i put it in reverse, when i pull up to a stop it dies when i put on the gas and try to take off. if I'm on a straight away and give it gas it will start to pick up then start cutting out. then engine sounds a little off but almost fine but there it a slight squealing like from a belt but i can't tell. any suggestions on what this might be?