I have to agree with marty , some time ago we had a fiesta with the same problem , swapped coil , still missing , removed PCM and checked wiring from PCM to coil , all ok , then we replaced pcm and it was ok , must of been a faulty driver within the pcm , but just double check everything before going down the pcm route .

They have a tamper proof bolt holding the wiring in so you will need to drill that out to check wiring , and dont forget once you have swapped PCM's you will need to recode keys , unless you get the matching key with PCM then you might get around it .

Hope that helps