[Celt03]

The plug wire defect was in the area of how the plug & wire seated together.
Point is - any part can be defective.
And often it is the simple (& inexpensive) things that cause some of the biggest problems.
We have learned - check the simple things FIRST.

Another scenario - a minute crack in the ECM that is not visible to the eye could also cause this type of problem.
We know of a case that it took almost 6 months to track that problem down. The heat causes the crack to expand & run rougher - cooled down - still rough. Eventually - crack will become larger & larger - then the car will begin to stall.