Older vehicles, up to about 1974, require a tune-up to maintain performance. However, modern vehicles will have a diagnostic computer system that will simply turn on the check engine light.
If the vehicle's check engine light is on, it could be running at a low fuel economy. Sometimes the computer can temporarily compensate for the problem, providing the opportunity to take the vehicle in for service. By reading information stored in the computer, we can perform the recommended tests to iscolate the problem and repair it.
With older cars, built before computer diagnostics, a tune-up consists of: