It frequently happens that the problem exists that defies the computer to put a label on it. Problems such as these are tough to locate at best. Typically, these problems include cam and crank sensors, airflow meters, ignition modules, etc. Under these conditions, it is best to check the most likely sources w/ an o'scope, looking at the waveforms. Though the most frequent, and easiest to fix are the connection, ground issues, which should always be checked first. Ford calls it the wiggle test, I call it necessary. The dealerships are typically the ones least able to help; they typically have little concern for the tech, leaving him to hold the bag. Ray