If you suspect the ignition system, here is something to look at. Right behind the battery is a small component that has large letters EDIS-x on it; probably EDIS-4. That is what actually makes the ignition coil pack fire the plugs, & is commonly called an 'igniter'. They are fairly reliable, but still there are electronics in it. They are expenive to buy new, but really easy to get from a car in a junkyard - I have gotten one for $5 at a pick-n-pull. I carry it on long drives as a spare, though I have never had one fail.
But the reason I mention it;...it has a large connector plugged into its bottom. On two my Escorts there is a large nylon cable tie wrapped around the EDIS, in a way to hold the connector snugly seated. If that connector worked loose, it could easily lead to misfiring of the spark plugs.