Lo and behold, the engineer found the phenomenon exactly as the customer had reported - the car seemed to have a specific allergy to vanilla ice cream. After several trials, the engineer noticed something - whenever the customer went into the store for vanilla ice cream, he took much less time to return back to the car than for other flavors. The reason, as the engineer found out, was that the vanilla, being a popular flavor, was stored for easy and quick access. So, it took less time than other flavors. Once this was known, the engineer quickly homed in on the cause - vapor lock.
Vapor lock in the hot engine prevented the car from starting.
When the customer bought vanilla and returned, the engine had not cooled enough for the vapor lock to disappear. The key is human expertise. As organizations grow in size and complexity and grapple with staff turnover, locating the expertise in time to solve a business or technical problem is anything but easy. The answer lies in how organizations learn to manage the information that they have and render it as knowledge to potential users - knowledge management. Organizational memory, especially in the software world, tends to be short.