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Tune-up
How do we perform a tune-up today? Is it strictly preventive maintenance? A diagnostic service? An emissions/OBD II checkup? Or, do you consider all of these things?
Some items have to be replaced every so often to keep an engine running properly. These include ignition, fuel and emission components that wear out or degrade as the engine accumulates miles. Most tune-up lists include new spark plugs, distributor cap and rotor, fuel filter, air filter and PCV valve. Any additional parts such as plug wires, an oxygen sensor, etc. are usually considered "extras" and are only replaced if the original part is defective, isnt performing up to par or is scheduled for replacement (an OHC timing belt or oxygen sensor, for example).
Spark plugs check for cylinder misfiring probable fouled or shorted spark plug, a shorted or loose plug wire, a bad fuel injector or loss of compression.
Visually inspecting the spark plugs : Things like oil consumption and abnormal combustion. Black, oily deposits on the plugs, for example, would tell you oil is being sucked past worn valve seals and guides. A slightly hotter spark plug might be recommended to improve low speed fouling resistance for city stop-and-go driving. If you find one or more plugs that are glazed or damaged, its a sure sign that detonation is occurring. This, in turn, could mean the engine is running too hot, that spark timing is over-advanced, that the EGR system isnt working properly, or that the customer has been buying cheap, low-octane gas.
Plug wires Check the condition of the wires visualy to determine if any of the plug wires are burned, chaffed, cracked, loose or damaged. Wires with loose or damaged boots or ones that show signs of age deterioration should be replaced to restore ignition reliability.
Distributor cap and rotor Visual inspections of these ignition parts is often the only way to find the source of an ignition-related case of misfire or hard starting. On engines with distributorless ignition systems (DIS) or coil-on-plug ignition, a visual inspection of the coils and wiring connectors will sometimes reveal cracks, carbon tracks or corrosion that can cause intermittent ignition problems.
Battery charging voltage Check alternator belt is tight and in good condition, or if the alternators charging curve is within normal specifications. A diode failure may allow the alternator to continue producing voltage, but it may not have enough output under high load conditions to keep the battery fully charged. Be sure to inspect the alternator drive belt and recommend a new one if the belt shows signs of age (cracks, flakes, glazing, etc.).
Battery condition Check