Scheduled maintenance (BMW 3 Series E46)

1. If the maintenance schedule is followed from the moment the vehicle is purchased, the fluid levels in the systems are checked regularly and frequently enough, and frequently worn parts are inspected, as recommended in this manual, then the vehicle will always be in working order and the need for additional work will be minimal.

2. However, there may be times when the engine will start to malfunction. Such situations are more likely when buying a used car that has not previously undergone frequent and regular maintenance. In such cases, it is necessary to perform maintenance immediately and regardless of the schedule.

3. The first step in diagnosing an engine whose serviceability is in doubt is to check the compression. Such a check (see chapter 2) will provide a large amount of information about the condition of the parts inside the engine and can serve as the basis for making a decision on the need for engine maintenance or repair. If, for example, a compression test indicates wear of the cylinder-piston group, then regular maintenance will no longer help and will only be a waste of time and money. Due to the special importance of checking the compression, the car owner must have the appropriate device in his tool kit and know how to use it.

4. If the engine is running unsteadily and malfunctioning, in most cases the following steps can help it.

Minimum amount of checks

• a) Clean, inspect and test the battery (see Weekly Checks).
• b) Check all engine related fluids (see Weekly Checks).
• c) Check and adjust the belt tension (paragraph B)
• d) Replace the spark plugs (paragraph 19).
• d) Check and, if necessary, replace the air filter (paragraph 20).
• e) Check the fuel filter (paragraph 23).
• g) Check all hoses under the hood for damage and leaks (paragraph 5).

5. If the above operations do not produce the desired effect, perform the following additional checks.

Complete inspection program

In addition to the above steps, perform the following operations.

• a) Check the battery charging system (see chapter 5).
• b) Check the ignition system (see chapter 5).
• c) Check the fuel system (see chapter 4)