There are several things that can cause your 2003 or Expedition to misfire. The most common cause is a plugged catalytic converter.
Bad plugs, wire , or coil pack.
Most likely a bad coil (each cylinder has one) located at the top of each spark plug
Most likely a bad ignition oil. Each cylinder has its own coil mounted at the top of the spark plug
I had the same problem on mines 98 Ford Expedition 4.6L . It ended been a simple tune up of plugs and wires. If it is a 5.4L it maybe a bad coil pack. I would switch the bad coil with a good one and go from there.
i have a 1998 ford expedition and i had simaliar to the same problem. does it feel like your loosing power? on my truck it was a misfire on my engine coil i would get that check out
Yes.
It could.
usually a misfire is either the spark plug or coil pack for that cyl. first I would change plug then change coil pack Take to dealer is still under waranty? Try replacing spark plugs.
A defective aspirator valve would unlikely cause a misfire monitor failure. It would more likely cause an air system monitor failure
If you have a "check engine" light on, start with having the codes read. A misfire code can tell you which cylinder or cylinders are having problems. A misfire could be the cause of your engine vibration.
With multiple misfires originating from the same coil pack, my guess would be to replace the driver's side coil pack.
There is no 95 Expedition. The first year was '97.