I remember seeing something on Youtube related to this. It was a Ford, but not an Expedition. Anyway, the video was about a faulty exhaust temperature sensor preventing the engine from idling. Do a search on Youtube for "Ford won't idle" and see what you get.
Basic approach would be to make a quick check for serious vacuum leaks, such as a loose hose off the power brake booster---then do a scan and see if anything turns up as a stored trouble code.
Will it stay running if you step on the gas?
Could be lots of things going on here, and methodical diagnosis is required. Could be idle air valve, fuel pressure issue, faulty coolant temp sensor---the list goes on.
Answers
Will it stay running if you step on the gas?
Could be lots of things going on here, and methodical diagnosis is required. Could be idle air valve, fuel pressure issue, faulty coolant temp sensor---the list goes on.