Computer runs engine rich on cold start, colder the temp richer it needs to be, thats what Choke plate did on carb enegines.
Rich mix needs hot spark to ignite it, your '87 should still have distributor and TFI ignition system, I would look at that, TFI systems are very old now, wires and parts fail.
Good read here on the TFI system: Ford EEC-IV/TFI-IV Electronic Engine Control Troubleshooting
Not sure what an "IAP sensor" is?
Also as a heads up, when you do any work on a computer controlled engine, disconnect the battery's negative cable.
Yes, it is for safety, BUT..........this will also cause computer to reboot when restarted, it will then "look" for any changes to the system, like new sensors.
Computers learn engine operation, changes in sensor data as they get older, so if you replace a sensor computer won't see that right away, it runs engine using old data because new sensor data isn't the same.