One problem related to ignition coils failure has been reported for the 1999 Ford Expedition. The most recently reported issues are listed below.
My 1999 Ford Expedition has had to have the ignition coil packs replaced at least 4 times. The symptoms are misfire and a resulting severe engine vibration upon acceleration. Once the vehicle reaches a cruising speed, the problem appears to go away, but only until you accelerate again. Ford motor company knows there is is design flaw in these vehicles which causes water dripping from some source (the air conditioner or a windshield that is not sealed) to short out the ignition coil packs. They have a technical service bulletin out on the problem, but the problem is not always reported as a check engine light and they fail to diagnose this properly in some cases. The first 2 times this happened, I took the car to two different Ford dealerships. Both trips cost me close to $400 each time. The third time it happened, we went to our local garage and the guy said this was a common problem, well known to auto mechanics, but that the individual failing cylinder could not be readily diagnosed by the computer codes, so it was an expensive repair because they might have to try all 8 coil packs to locate and identify the offender. The last coil pack that failed was replaced by my husband at a cost of $45. 00 as the failing unit was easily accessible. You can see the great difference in cost of doing it yourself vs. Both of my trips to the dealership. My truck is failing again now and of course, it is exhibiting the same symptoms of a coil pack failure. This time, however, the coil pack in question is not easily accessible for the home mechanic and we will be forced to take it in for repair.