If I remember right this is the advise you got last time. AND STILL YOU HAVEN'T LOOKED AT THE PLUGS. What I am wondering is if you cann't remove the plugs for fear you will screw-up the threads, then what are you able to do. As far fixing the car. Pulling spark plugs when they are easily accessible is one of the most basic auto repair/maintance tasks.
1) you have a mis fire. Check your plugs see if one is damaged,fouled, MISSING
2)You get SH!TTY gas mileage. Check your plugs see if one is damaged,fouled,MISSING.
Without looking you cann't be sure. At first maybe it was the coil. Now you changed that well what do you know it still has a mis fire cause the plug is fouled and still wont spark. Even tho the first cause has been fixed the problem continues its Possible. I'm done with this. So good luck:lol: