Multiple Cranks to Start when Cold
 

I have a 2006 Ford F150 XLT (4.6l) which I am very happy with. Over the past year, I've been having some problems with starting when cold and idling. When the car has been sitting for a while or over night. It takes 2 -3 cranks for the engine to catch. It seems as if it fuel is not in the rail and the numerous cranks primes it. Also I noticed that at idle, the engine seems to stumble as if one of the cylinders misfires every once in a while. At speeds it runs just fine. I'm not too sure of what to make if it. If it's a bad plug then wouldn't it miss even at speeds? I thought maybe a dirty fuel injector so I have been using Lucas Oil Gas Treatment/Fuel Injector cleaner for the past week. Maybe this will take care of the stumbling problem at idle.

Over the past year and a half I've replaced the plugs, fuel pressure sensor, fuel pump driver module (FPDM) & most recently the ignition coils. I suspect it's the fuel pressor sensor since reading about it, it's main purpose is ensure there is adequate fuel pressure in the rails. I don't think it's the fuel pump since everything I was reading suggests that if the pump is failing it would be under all conditions not just at idle. I just don't want to start replacing things hoping this will fix it.

If anyone has any experience with this, I would be grateful if you would jump in with some advice. Thanks.