Intermittent

A problem that comes and goes away with no obvious pattern.

Intermittent problems are the most difficult to diagnose and repair on vehicles today. The amount of electronics that control everything from engine management and emissions means there are a lot of problems that can be intermittent.

Actually any system that has has electronic sensors or controls in it is susceptible to an intermittent problem. These can be caucused by loose wiring connection, faulty sensors or computers.