Tune-Up Procedures

Introduction
The word "tune-up" actually applies only to older cars, on which you can perform the traditional work associated with the term-spark plug replacement, ignition contact point replacement, dwell adjustment, ignition timing adjustment and carburetor idle and mixture adjustment. For most of today's cars, “engine performance maintenance” is a more accurate term. All modern cars and light trucks are equipped electronic ignition (no points) and at least one on-board computer that automatically adjusts items like the ignition timing, fuel mixture and idle speed. In fact, on modern computer-controlled cars, it's impossible to adjust these yourself.
An automotive tune-up is an orderly process of inspection, diagnosis, testing, and adjustment that is periodically necessary to maintain peak engine performance or restore the engine to original operating efficiency.
On an electronic ignition system, the basic tune-up procedures are as follows:

• Remove spark plugs
• Test compression in each cylinder.
• Clean and/or replace spark plugs and gap spark plugs to manufacturer’s specifications and install in engine.
• If applicable, check the distributor cap and rotor for cracks and wear. Replace if necessary.
• Use tachometer to set idle speed to specifications (if adjustable).
• Use timing light to set initial timing (most electronic ignition systems do not require adjustments).

The list above represents only the “bare bones” facts about tune-ups. Other functions that could be performed are using an emissions analyzer to check for compliance with emissions standards and for fuel economy, and measuring vacuum and checking for leaks with a vacuum gauge.
The tune-up is also a good opportunity to perform a general preventive maintenance check on everything in the engine compartment, and look for failed or about to fail components such as loose or damaged wiring, leaking fuel lines, cracked coolant hoses, and frayed belts.
The purpose of this section of the ProCarCare Maintenance Guide is to provide the non-mechanic with some simple inspections he or she can perform without specialized tools – chiefly on spark plugs, which can indicate many kinds of engine problems. This information is intended as a guide to use in talking with your service center. If you’re a do-it-yourselfer, you’ll want to obtain a car-care manual for your year, make and model of car for the actual tune-up procedures.
Spark plugs Spark plug life and efficiency depend upon the condition of the engine and the combustion chamber temperatures to which the plug is exposed. These temperatures are affected by many factors, such as compression ratio of the engine, air/fuel mixtures, exhaust emission equipment, and the type of driving you do.
Factory installed plugs are, in a way, compromise plugs, since the factory has no way of knowing what sort of driving you do, but most people never have reason to change their plugs from the factory-recommended heat range.