Engine Tune-up

Tool and Supply Checklist: 

• Service manual
• Battery clamp cleaning tool
• Masking tape
• Spark plug socket and ratchet
• Spark plug gauge
• Dwell meter
• Oil, oil filter, and oil pan
• Power timing light
• Rags
• Knife
• Screwdrivers
• Allen wrench
• Feeler gauge
• Safety glasses or goggles

Tune-up is to restore the engine to the performance level recommended by the auto maker. Tune-up involves replacing parts that are close to or have already reached the end of their useful life. Tune-up also involves servicing the parts to reliable conditions. Various engine systems must be adjusted to meet the auto maker's specifications and keep them performing effectively.

A complete (major) tune-up should be performed every 10,000 to 12,000 miles on cars with contact ignition systems, or every 15,000 to 20,000 miles on cars with electronic ignition systems. Please refer to the service manual, tune-up specification book, or Vehicle Emission Control Information (VECI) decal located under the hood of your car for specifications.

Tune-up tasks:

• Change oil and oil filter, air filter, and fuel filter
• Check battery fluid level and clean the battery posts and clamps
• Check PCV valve, vacuum hoses, and electric connections
• Check for loose, cracked, or hardened spark plug wires. Replace the whole set of spark plug wires every three years.
• Replace spark plugs
• Replace distributor cap and rotor
• Adjust idle speed
• Adjust ignition timing
•  

Replace spark plugs:

Replacing spark plugs is the most critical tune-up procedure. 

1. Pull off spark plug wires by carefully grasping the boot and twisting it back and forth. Work one plug at a time to avoid mixing up the wires.
2. Label each plug with masking tape so that it is reinstalled on the correct cylinder.
3. Use a spark plug socket and ratchet to remove the plugs. If the plugs are hard to reach, you might need extensions and universals. CAUTION: Make sure to center the plug in the socket. If held at an angle, the socket could break the plug insulator.
4. Set the gap on the new plugs using a spark plug gauge. Look up the tune-up specifications for your car to determine the correct gap.
5. Turn the plugs into the holes by hand. Finger tighten them another 1/8 of a turn with the socket wrench. Do not over-tighten.

Adjust idle speed:

If your car has a computer-controlled ignition system, refer to the service manual or the VECI decal under hood for instructions on setting the idle speed.

On cars with conventional systems, locate the idle set screw at the throttle linkage or anti-dieseling solenoid. Turned clockwise, it decreases idle speed. Turned counterclockwise, it decreases idle speed.

Keep the following points in mind when adjusting idle speed:

1. Make sure the engine is fully warm and off the fast idle cam when adjusting the curb idle.
2. If the idle is set with air cleaner off, double check it with the cleaner unit in place.
3. Never try to smooth out the idle by turning up the speed. Higher idle speed just wastes gas and causes dieseling.

Adjust ignition timing:

You are now ready to make the final and most important adjustment - ignition timing.

1. Hook up a power timing light. Attach the red lead to the positive battery terminal and the black lead to the negative terminal.
2. The third lead has a special connector that attaches to the number one cylinder plug wire. The service manual will show the location of the number one cylinder pickup at the distributor cap.
3. Look up the service manual for the location of the timing marks. Rotate the engine by hand or tap the ignition switch until the marks are visible.
4. Clean the dirt off the timing marks with solvent to see them better.
5. Very carefully make a neat line with white chalk or white enamel paint over the correct timing mark. This will help you see the mark when the engine is running.
6. Start the engine and let it warm. The engine must be fully warmed and idling at the proper speed to set the timing.
7. While the engine warms, check the service manual or the VECI decal under hood to see if there are any special timing procedures. Most engines with contact ignition systems must be timed with the vacuum advance line removed at the distributor and plugged. The best way to do this is by attaching a vacuum gauge in the end of the line.
8. Aim the light carefully at the timing marks. Keep the light at about a 45º angle and sight directly down the light. CAUTION: Stay away from the cooling fan blades at all time.
9. The light flashes when the number one cylinder fires and makes the timing marks appear to stand still. The specified mark and timing pointer will align on each flash if the engine is in time.
10. If the mark and timing pointer do not line up, you will have to adjust the timing by rotate the distributor. To do this , first loosen the clamp bolt that holds the distributor in place.
11. To adjust the timing, rotate the distributor slowly until the timing mark and pointer align. Then carefully lock down the clamp bolt and double check to make sure the settling did not change when the distributor was tightened.