2. When searching for the causes of engine malfunction (for example, a drop in the developed power) it always makes sense to check the compression in the cylinders (see Chapter 2). Also make sure that the air and fuel filters are replaced according to the maintenance schedule (see Chapter 1).
3. Check the reliability of the wire ends on the battery terminals, and make sure there are no signs of oxidation of the terminal connections. If necessary, take appropriate troubleshooting measures and replace any faulty components. Examine the condition of the grounding buses and their terminal connections equally carefully - the contact surfaces of the corresponding ground elements (powertrain/body panels) must be absolutely clean and free from traces of corrosion.
4. Carefully inspect all visible electrical wiring inside the engine compartment, check the reliability of the contact connections. Replace any wiring that shows obvious signs of damage, ensuring that the harnesses are routed correctly; if necessary, tighten the loose fasteners of the components on which the insulation has rubbed through.
Note: The risk zone is always the area of electrical wiring that runs near components that have been serviced most recently.
5. It should be remembered that the conductive wires of the electrical wiring may be damaged in the absence of signs of damage to the insulation; in such a situation, an external inspection will not yield positive results. Such damage can occur as a result of wires being pulled out or when their routing is disrupted.
6. Damaged electrical wiring can be repaired by soldering a shunt wire onto the broken section - soldering ensures reliable electrical contact. To repair the insulation, use insulating tape or place a piece of heat shrink tubing on the wire. The best (although not the cheapest) the way to eliminate all failures associated with damage to electrical wiring is to replace the faulty wire.
7. Once the repair/replacement is complete, ensure that the appropriate harnesses are routed correctly, paying particular attention to areas of the routes that pass near hot surfaces and moving components in the engine compartment. Make sure that the harnesses are securely fastened in all the provided intermediate fasteners.
8. Check the condition of all accessible terminal connections, check the reliability of the electrical wiring connectors. If traces of corrosion are detected on the inner surface of the connector (white or green deposits, rust coating), and in case of excessive contamination, remove the connector from the corresponding terminal and clean it thoroughly, using a special spray if necessary. Seriously damaged connectors must be replaced, in some cases along with the wiring harness.
9. After cleaning the connector from corrosion, pack it with preservative grease before installing it in place.
10. The TDC position of the piston in cylinder 1 is determined by the crankshaft position sensor (CPS). Excessive contamination or dust on the sensor may cause misfires.
11. Carefully inspect the hoses and tubes of all vacuum lines in the engine compartment. Check the tightness of the fastening clamps, and ensure there are no deformations, cracks, cuts, delaminations, or other physical damage to the hoses and tubes. Carefully examine the fittings for signs of leakage (see Chapter 1).
12. Assess the condition and check the PCV system hoses for leaks. Excessive contamination or obstruction of the hoses will result in unstable engine speed, especially at idle.
13. Moving from the fuel tank to the fuel distribution line (through the fuel filter) along the fuel lines, carefully examine the condition of the fuel lines. Pay special attention to the joints of the pipes, where cracks most often form, through which leaks begin to develop. Replace damaged sections of fuel lines.
14. Check the condition of the air cleaner filter element. An excessively dirty filter can significantly increase the total aerodynamic resistance of the intake air tract, which directly affects the power developed by the engine. Replace the filter element if necessary.
15. Start the engine and let it idle.
Caution: When performing any work in the engine compartment with the engine running, exercise extreme caution - try not to touch the hot surfaces of the power unit and exhaust system, do not allow hair and clothing to get caught in moving components (cooling system fan, accessory drive belt)!
16. Moving from the air intake to the air cleaner and further to the throttle body, make sure there are no signs of air leaks developing in the intake tract. To identify sources of leaks, you can use a soap solution. Correct the violations.
17. Place the vehicle on a lift and inspect the exhaust system components. Check for signs of developing leaks. The easiest way to detect exhaust leaks is by plugging the exhaust outlet. A characteristic whistling sound and smoke will help pinpoint the damaged area. Tighten loose clamps/replace failed gaskets, replace damaged sections.
18. At the final stage of testing, with the engine running, pull the contact connectors of its electrical wiring one by one - a change in the nature of the engine's operation will indicate poor contact quality - make the necessary corrections, replace the faulty sections of the electrical wiring.
19. If, during the preliminary checks, it is not possible to identify the cause of the engine malfunction, the vehicle should be taken to a service station for a more thorough diagnosis using special equipment.
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