General information
The ignition system of the gasoline engine is integrated with the fuel injection system and controlled by a single ECM (see chapter Power supply systems, release and reduction of toxicity of exhaust gases).
The ignition system and the fuel system have a common diagnostic system designed to detect violations, store fault codes and find the causes of failures. When a fault occurs, the control module writes to the processor memory.
The cause of engine malfunctions can most often be located by reading the data stored in the memory of the ECM self-diagnosis unit. After the failure is identified, you can proceed to check the status and proper functioning of the relevant components and components. Remember that a visual check of the condition of the wiring and its contact connectors is not enough - be sure to read the information stored in the memory of the control module.
Preliminary checks
If a malfunction occurs shortly after servicing a component, first of all, carefully check the corresponding element. Perhaps the reason lies in the carelessness of installing the component or connecting the electrical wiring connector to it.
When investigating the causes of a drop in engine power, in addition to the checks listed below, also check the compression pressure in the cylinders (see chapter Engines). It is possible that the reason for the decrease in the efficiency of the return of the power unit lies in a careless attitude to the implementation of such regular vehicle maintenance procedures as replacing the fuel filter or air cleaner filter element (see chapters Vehicle settings and routine maintenance, Engines and Power supply systems, release and reduction of toxicity of exhaust gases).
Remember that after reading the trouble codes, the module memory must be cleared. Clearing the memory is done using the same device that is used when reading the codes (see Section OBD system - general information).
1. Open a cowl and check up reliability of fixing of tips of wires on pole plugs of the storage battery. Make sure that there are no signs of oxidation of the terminals, if necessary, clean them (see chapter Vehicle settings and routine maintenance). Check the reliability of fixing the terminal connections of the grounding buses and the quality of the electrical contact in them - the mating surface must be absolutely clean and free from oxidation products.
2. Carefully inspect all visible wiring inside the engine compartment, check the reliability of all electrical connections - pay attention to obvious signs of damage. In case of detection of cracks, cuts, abrasions of the insulation, replace the defective elements. A wire break can occur as a result of careless installation of any node - the wire can melt on contact with the elements of the exhaust system. The most likely cause of wiring damage is improper wiring in the engine compartment after performing repair or maintenance procedures for any component.
3. Wiring may be damaged or shorted even in the absence of obvious damage to the insulation, and external inspection will not give results. This kind of damage can occur after pulling wires or improperly placing harnesses in the engine compartment.
4. Damaged wiring can be restored by soldering a piece of a new conductor into the gap - soldering is a necessary condition that guarantees a reliable contact. Repair of damaged insulation is usually carried out using a sufficient amount of electrical tape, or a piece of heat shrink tubing. If the damage is significant, or the damaged wire plays a significant role, the most correct (although quite expensive) the solution is to replace the corresponding harness.
5. After repairing the damaged electrical wiring, make sure that it is laid correctly in the engine compartment - the harnesses should not touch the heated surfaces of the power unit. Do not forget to secure the wires in all provided intermediate clamps.
6. Check up a condition and reliability of fixing of all accessible contact sockets. All fasteners must be installed. If oxidation products are detected on the inner surface of the connector (white or green deposits, as well as traces of metal corrosion) or signs of excessive contamination, disconnect it from the appropriate terminal and clean it thoroughly, preferably using one of the special cleaners - ask at car accessories stores. Severely damaged connectors must be replaced, sometimes complete with a wiring harness connected to it.
7. After removing all traces of oxidation and dirt, fill the connector with preservative grease (consult a car workshop) and install in place, - make sure the connector is securely fixed.
8. Standard on all models is a CKP inductive crankshaft position sensor that provides the ECM with information about engine speed and TDC position of cylinder #1. Contamination of the sensor head with oil or dust can cause misfiring. For a description of the procedures for removing and installing the CKP sensor, see Chapter Power supply systems, release and reduction of toxicity of exhaust gases.
9. Carefully examine the condition of all vacuum lines laid in the engine compartment. Check the tightness of the mounting clamps, make sure that there are no cracks, delaminations or other damage to the hoses. Inspect hoses for signs of obstruction (twisting, squeezing, bending, etc.). Pay special attention to hoses laid near sharp edges, as well as the condition of the sections pulled onto the fittings. Damaged hoses must be replaced.
10. Check the condition of the crankcase ventilation hoses (PCV). Make sure there are no signs of obstruction. The number of hoses and their location of the system may vary depending on the model of the car, however, in any version of the model, there is a hose connecting the top of the engine to the air intake sleeve or intake manifold. PCV hoses are usually connected to the intake manifold also to the cylinder block (or oil filler neck) and serve to transport crankcase gases and oil vapors to the combustion chambers. Blocking the patency of these hoses usually leads to a violation of the stability of the engine, especially at idle.
11. Moving along the fuel lines from the fuel tank to the fuel line, carefully examine the condition of the lines of the power system path and their union connectors. If there are signs of damage or deformation, replace the defective section. Particular attention should be paid to the condition of the junctions of the lines, where cracks are most often formed, leading to the development of fuel leaks.
12. Check the correct laying and adjustment of the throttle cable (see chapter Power supply systems, release and reduction of toxicity of exhaust gases). The cable should not bend too much. If there is a suspicion of a malfunction of the cable assembly, replace it.
13. Remove the cover of the air cleaner housing and check the condition of the filter element (see chapter Vehicle settings and routine maintenance), if necessary, blow out or replace the dirty filter, since an increase in its resistance to patency can lead to a noticeable decrease in the power developed by the engine.
14. Start the engine and leave it running at idle.
When performing any work in the engine compartment with the engine running, use extreme caution. Avoid touching hot surfaces of the power package and moving parts such as drive belts and fan impeller. Try to strictly observe all necessary precautions and safety regulations.
15. Moving from the air intake to the air cleaner and further to the throttle body, make sure that there are no signs of the development of leaks in the intake air path (including vacuum hoses). Leaks can be identified by a characteristic whistle - for greater reliability, moisten the suspected area with a solution of soapy water. If the hose is damaged, the behavior of the engine will change, and bubbles will appear on the treated surface of the hose (or, depending on the pressure in the hose, water may begin to be sucked in). If a leak is found, tighten the appropriate clamp or replace the damaged hose.
16. Drive the car onto a flyover / viewing hole (or jack it up and put it on stands) and carefully examine the condition of the components of the exhaust system from the exhaust manifold to the cut of the rear section. The sources of exhaust gas leaks are most easily identified by the appearance of a characteristic whistle when the system outlet is clogged - tighten the appropriate fasteners, or replace the burned-out section.
17. A further check is to alternately move each connector on the corresponding terminal with the engine running. The unreliability of the electrical contact will manifest itself by a change in the nature of the engine. Make the necessary corrections, replace failed components - some connectors are changed complete with wiring harnesses connected to them.
18. If during the listed preliminary checks it is not possible to identify the cause of the existing violation, the car should be driven to a service station in order to conduct a complete diagnosis of the control system using special equipment.
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