My 91 3.9 EA, had thottle body injection and it a carb as such.
The Car Clinic guy fixed a whole list of engine rev up, miss fire, rough running, rich mixture etc etc etc. Ford had no idea "the computer said it's fine" was always the reply.
They did the old fault finding by replacement trick on me to start with, O2 senser, themostat, MAP senser,power steering switch,and a couple of others I forget the name of $$$$$$$$$.
John did a lot of cleaning of earths and adding it a couple of extra ones and new ECU and pin cleaning got it running at about 98% but that last intermitant rpm rise he could not find what was causing the signal to the stepper motor.
John sure is switched on with EFI stuff so I don't think anyone could fully fix mine and bending the motor away gave me 100% engine running.
Guess the heavy handed taxi fix worked, a small price to pay for smooth running.
Mileage was 380,000 and she's still sweet at 435,000, I asked my friend who now owns it.

Yeh, its a CFI engine. In regards to the power steering switch, i had pulled out my whole steering wheel one time to install my central locking. Maybe i've changed something. So i'll check all the wires over and replace em i guess. Thanks for the tips.

so the CFI EA's will still work properly without the ISC motor, thank god mine was starting to piss me off, it "chimes" and sends the rpm's to over a 1000 (almost) every time you even breath on the throtle.

check the neoprene seal in the ISM if damaged, it will not seal - hence high idle - pretty common when on gas.