GM Full-Size Trucks 1980-1987 Repair Guide

Engine Electrical


In order to extract the full measure of performance and economy from your engine it is essential that it be properly tuned at regular intervals. A regular tune-up will keep your vehicle's engine running smoothly and will prevent the annoying minor breakdowns and poor performance associated with an untuned engine.

Neither tune-up nor troubleshooting can be considered, independently since each has a direct relationship with each other.

It is advisable to follow a definite and thorough tune-up procedure. Tune-up consists of three separate steps:

  1. Determine whether normal wear is responsible for performance loss.
  3. Determine what parts require replacement service.
  5. Installation and adjustment of new or existing parts.

The manufacturer's recommended interval for tune-ups is 22,500 miles or 18 months, except for heavy duty emission models, which use the 12 months or 12,000 mile schedule in all years. These intervals should be shortened if the truck is subjected to severe operating conditions such as trailer pulling, off-road driving, or if starting and running problems are noticed. It is assumed that the routine maintenance described in Routine Maintenance has been kept up, as this will have an effect on the results of the tune-up. All the applicable tune-up steps should be followed, as each adjustment complements the effects of the others. If the 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. The light duty sticker is usually found on the underhood sheet metal above the grille. The heavy duty sticker is usually on top of the air cleaner.

Diesel engines do not require tune-ups, as there is no ignition system.

Troubleshooting is a logical sequence of procedures designed to locate a particular cause of trouble. Troubleshooting Charts in this book can be found at the end of each section where applicable and are general in nature (applicable to most vehicles), yet specific enough to locate the problem.

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.