### Tune-Up Tools

NOTE: The word "tune-up" actually applies only to older vehicles, on which you can perform the traditional work associated with "tune-up" — spark plug replacement, ignition contact point replacement, dwell adjustment, ignition timing adjustment and carburetor idle and mixture adjustment.

For today's vehicles, engine performance maintenance is a more accurate term. Modern vehicles are equipped with electronic ignition (no points) and an on-board computer that automatically adjusts the ignition timing fuel mixture and idle speed. In fact, on modern computer-controlled vehicles, it's usually impossible to adjust these yourself:

If you plan to do your own engine performance maintenance, there are some specialized tools you are going to need. You'll need a round wire gauge to check and set the plug gap, a timing light (if your ignition timing is adjustable), a dwell-tach or just a tach (to set idle speed if it is adjustable). A compression gauge is also handy, though not necessary.

An important element in checking the overall condition of your engine is to check compression. This becomes increasingly more important on high mileage vehicles. Compression gauges are available as screw-in types and hold-in types. The screw-in type is slower to use, but eliminates the possibility of a faulty reading due to escaping pressure. A compression reading will uncover many problems that can cause rough running. Normally, these are not the sort of problems that can be cured by a tune-up. Vacuum gauges are also handy for discovering air leaks, late ignition or valve timing, and a number of other problems.

Fig. 15: Two styles of compression gauges. The screw-in type on top is more accurate and is easier to use, but is more expensive.

Fig. 16: A variety of tools used for spark plug installation and timing adjustment