Hello I have a 1991 F150 5.0 that has 1 problem I cannot figure out. When I start my truck after it sits a while or overnight it idles like it has a huge vacume leak for just a min. I can hold it at 1500 rpms for just a min and it idles fine after that cut it off start it back and its fine anyone have any clue what this could be? Ive replaced Iac,ect,map,hego,fpr,dizzy cap,wires, plugs,checked timing, seafoam. No codes Maybe a leaking injector??

 

Sounds like your fuel pressure is dropping