Tune-up general information
The term tune-up is used in this manual to represent a combination of individual operations rather than one specific procedure. If, from the time the vehicle is new, the routine maintenance schedule is followed closely and frequent checks are made of fluid levels and high wear items, as suggested throughout this manual, the engine will be kept in relatively good running condition and the need for additional work will be minimized. More likely than not, however, there will be times when the engine is running poorly due to lack of regular maintenance. This is even more likely if a used vehicle, which has not received regular and frequent maintenance checks, is purchased. In such cases, an engine tune-up will be needed outside of the regular routine maintenance intervals.
The first step in any tune-up or engine diagnosis to help correct a poor running engine would be a cylinder compression check. A check of the engine compression will give valuable information regarding the overall performance of many internal components and should be used as a basis for tune-up and repair procedures. If, for instance, a compression check indicates serious internal engine wear, a conventional tune-up will not help the running condition of the engine and would be a waste of time and money.
The following series of operations are those most often needed to bring a generally poor-running engine back into a proper state of tune.
Minor tune-up
Check all engine related fluids (see Fluid level checks)
Clean, inspect and test the battery (see Battery check, maintenance and charging)
Check all under hood hoses (see Underhood hose check and replacement)
Check the cooling system (see Cooling system check)
Check the air filter (see Air filter replacement)
Check the drive belts (see Drivebelt check and replacement)
Major tune-up
All items listed under Minor tune-up, plus.
Replace the air filter (see Air filter replacement)
Check the fuel system (see Fuel system check)
Replace the spark plugs (see Spark plug check and replacement)
Check the charging system (see Engine electrical systems)