Problems & Fixes
It's a sure bet that the under hood Electronics which are subjected to the engine heat will eventually fail. So I find that any electronic equipped car like the 83 up Fords, may start to experience problems after the 100k miles point.
The first two things to fail are the TPI (throttle position sensor) mounted on the CFI & the TFI (thick film ignition), mounted on the Distributor.
When I got my 84 Police LTD with 150k miles on it, while cruising on the Freeway it would start jerking so bad that I had to get off the Freeway & limp home on the surface streets. Have heard this from others too. Replaced the TPI & TFI & no more problem.
Of a lesser problem is the MAP (manifold absolute pressure). Two easy checks for it is first to remove the vacuum line & see if there is any Green Snot coming out the port. This is caused by a internal Vacuum leak that sucks out the more solid gel that is used to pack the inside if the module. If there is no snot at the port, using a hand Vacuum pump to pull a vacuum on the port. There should be no leak down.
If you plan on getting a "new" MAP from the junk yard, take your Vacuum pump with you. I am real surprised but I have found no real difference in the "Vacuum in Frequency out" of any of the "Fox" MAP's. This includes 4 cyl, 4 turbo, 6 cyl, 5.0 HO & non HO. Even the later ones not connected to the Vacuum line , but open to the atmosphere. I noticed this when looking for a different acting one to modify the performance of my a bit too modified, still CFI engine. I even opened a couple up to modify with added resistors or capacitors, but nothing changed. However, their may be small differences between them & would only use one from a different engine to experiment or in an emergency, not for daily driving.
Next will be what a non or bad Diode protected Starter Relay may do to your EEC!