The first coil was replaced in November of last year. At that time, the car backfired and then the check engine light began to blink. Then two more coils were replaced on the third attempt (early June) to fix the “throttle control” warning light. I was told that they tested the coils individually and that those two failed their “stress” test. At that point, I asked if it would be a good idea to replace the remaining three. I was told no because they did not fail the test. Then a couple of days later, my car did the exact same thing and I brought it into the shop. This time they stated that the last three coils failed their most recent round of testing and needed to be replaced. At that point, I thought it was very coincidental that all six coils would fail within 6 months of each other, so I called Ford to register a complaint. Now that the car is again in the shop for the VERY SAME reason, they are suspecting that the alternator is sending an intermittent spike through the system, which has caused the coils to fail at different times.