Neither tune-up nor troubleshooting can be considered independently since each has a direct relationship with the other.
It is advisable to follow a definite and thorough tune-up procedure. Tune-up consists of three separate steps: Analysis, (the process of determining whether normal wear is responsible for performance loss, and whether parts require replacement or service); Parts Replacement or Service; and Adjustment, (where engine adjustments are performed).
The manufacturer's recommended interval for tune-ups on non-catalyst vehicles is 15,000 miles (24,000 km). Models with a converter, every 30,000 miles (48,000 km). Models equipped with a 2.6L engine require a valve lash adjustment every 15,000 miles (24,000 km). This interval should be shortened if the vehicle is subjected to severe operating conditions such as trailer pulling or stop and start driving, or if starting and running problems are noticed. It is assumed that the routine maintenance has been kept up, as this will have an effect on the result of the tune-up. All the applicable tune-up steps should be followed, as each adjustment complements the effects of the other. If the tune-up (emission control) sticker in the engine compartment disagrees with the information presented in the Tune-up Specifications chart in this section, the sticker figures must be followed. The sticker information reflects running changes made by the manufacturer during production.
Troubleshooting is a logical sequence of procedures designed to locate a particular cause of trouble. While the apparent cause of trouble, in many cases, is worn or damaged parts, performance problems are less obvious. The first job is to locate the problem and cause. Once the problem has been isolated, repairs, removal or adjustment procedures can be performed.
It is advisable to read the entire section before beginning a tune-up, although those who are more familiar with tune-up procedures may wish to go directly to the instructions.