98 expediition check engine light

:runaround:i have a 98 expedition with a 4.6 and a check engine light came on ran the codes and i have 1506 in the book that code it says it's a (idle air control IAC over speed error) do i need to chage the IAC valve and if so were would it be located at. And it also shows codes 171 and 174 ( system to lean banks 1&2) is that from the IAC valve any help would be great thanks

I think I would focus on the lean codes first. There no disputing the fact that the intake gaskets leak on these. Very easy to find with a smoker but you can also carefully spray carb cleaner around the intake and listen for an rpm change. Carb cleaner is flammable!!! Please keep that in mind if you go that route!!!

I think I would focus on the lean codes first. There no disputing the fact that the intake gaskets leak on these. Very easy to find with a smoker but you can also carefully spray carb cleaner around the intake and listen for an rpm change. Carb cleaner is flammable!!! Please keep that in mind if you go that route!!!ok i sprayed one can of carb cleaner and half a can of brake cleaner and no change in idle i thought the newer expeditions had that problem can the iac have anything to do with 171&174 codes