The ignition system and the power system are interconnected components of the engine management system. Therefore, some components perform several functions related to the functioning of different parts of the engine management system.
General information
The ignition system and fuel system share a common diagnostic system for storing fault codes and performing diagnostics. When a malfunction occurs, the control unit writes to memory a certain sequence of signals (fault code), which can subsequently be considered a special device (refer to the Section that describes the procedure for checking the fuel system).
If there are malfunctions in the car engine, the reason for this can most likely be found out by examining the memory of the control unit. After reading the fault codes, you can find out which node is faulty and perform the appropriate checks (either the node itself or its electrical wiring).
A visual check of the wiring and connectors is not enough - be sure to read the information stored in the memory of the control unit.
Preliminary checks
If a malfunction occurs shortly after servicing a component, check that component and its surroundings carefully first. Perhaps the reason lies in a carelessly installed component or an insecurely connected connector.
If you are trying to find the cause of a specific engine problem, such as a loss of power, in addition to the steps below, measure the compression in the cylinders. Make sure the fuel filter and air cleaner are changed at the prescribed intervals.
Keep in mind that after reading the fault codes, they must be deleted from the memory of the control unit using the same diagnostic scanner, and then the fault should be repaired.
Open the hood and make sure that the wire ends are securely connected to the battery terminals and that there is no corrosion on them. If signs of corrosion or damage are found, replace or clean the wires. Check all ground straps in the same way, making sure they make good contact (mating surfaces must be absolutely clean and free from corrosion) body or engine.
After that, carefully inspect all visible wiring laid inside the engine compartment. Make sure all connections are secure. At this stage, you are interested in clearly damaged wires. They can be cut or chafed by sharp or moving engine parts such as suspension parts or a drive belt. A wire break can occur as a result of careless installation of any node. The wire may melt on contact with the exhaust system. The most likely cause of wiring damage is improper routing of wiring harnesses in the engine compartment after repair or maintenance of any component.
Wires can be damaged or shorted without damaging their insulation. In this case, the inspection will lead to nothing. Similar damage can occur after wires are pulled or wires are incorrectly placed inside the engine compartment. If you think that such damage is possible, check the wire following the sequence below.
Damaged wire can be repaired by soldering a piece of new wire into the gap. Soldering is necessary to obtain a reliable contact. The insulation can be repaired with enough electrical tape or heat shrink tubing. If the damage is significant and the damaged wire plays a significant role, the most certain way out (although quite expensive) the corresponding harness will be replaced with a new one.
After repairing the damaged wire, position it properly in the engine compartment, away from rotating and hot components. Do not forget to fix the wire in the intermediate clamps (if there).
Make sure all accessible connectors are secure and clean. All fasteners must be installed. If you notice signs of corrosion on the inner surface of the connector (white or green deposits, as well as traces of rust) or excessive dirt, remove it from the corresponding terminal and clean thoroughly. To do this, you can use a special aerosol. If the connector is seriously damaged, it should be replaced. Keep in mind that in some cases you will need to replace the entire harness.
If you were able to completely remove the corrosion from the connector, fill it with preservative grease, then reinstall it. You can find out the type of lubrication at the service station.
All models have a crankshaft position sensor (it also determines the TDC of the first cylinder). Its working part may be contaminated with oil or dust, which can lead to malfunctions and, consequently, misfires.
Carefully inspect all vacuum hoses and tubes located in the engine compartment. Make sure that the clamps are securely tightened and that there are no cracks, delaminations or signs of damage on the hoses themselves. Also make sure that no hoses are kinked or bent too much, i.e. do not let air through. Pay special attention to hoses near sharp edges and to the ends of all hoses. All damaged hoses must be replaced.
Check for signs of damage and contamination on the hoses of the crankcase ventilation system. Also make sure they are not blocked from the inside. The number and location of system hoses varies by vehicle model, but all models have a hose that connects the top of the engine to the air intake hose or intake manifold. The system hoses also connect the cylinder block (or oil filler neck) with inlet pipe. These hoses deliver oil vapor to the combustion chambers. If these hoses are dirty or blocked, the engine will run unstable (especially at idle).
From the fuel tank through the fuel filter to the fuel distribution line along the fuel lines, carefully inspect them. If any signs of damage or kinks are found, replace the affected section. Pay special attention to the connection points of the pipes. Cracks may appear on them, leading to fuel leaks.
Remove the air cleaner housing cover and inspect the element. It should be relatively clean and dry. A heavily soiled purifier has a strong resistance to air flow, which leads to a noticeable decrease in engine power. Replace air cleaner if necessary.
Start the engine and leave it to idle.
Caution: When doing any work in the engine compartment with the engine running, use extreme caution. In addition to the high risk of burns from hot engine or exhaust system parts, you risk serious injury from rotating parts (e.g. radiator fan or drive belt). Before starting work, first of all take the measures and follow the safety precautions set out at the beginning of each Chapter. Watch your hands, do not let long hair or clothing get into the engine compartment. Stay away from the exhaust system and other hot parts.
Proceeding from the air intake to the air cleaner and on to the throttle, check that there are no leaks from the air supply hoses (including nearby vacuum hoses). They can be detected by a characteristic whistle. If no whistle is heard, apply a small amount of soapy water to the suspicious section of hose. 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, securely tighten the clamp or replace the damaged hose.
Check the entire exhaust system in the same way (manifold to rear section). Check for gas leaks. To facilitate the work, you can raise the car on a lift, install it on a flyover or over a pit. For the most basic test, plug the outlet of the exhaust system and listen for system operation. If you hear a characteristic whistle, there is a leak. If a leak is detected, tighten the appropriate clamp, bolts or nuts, replace the gasket or burnt section.
A further check is to alternately move each connector on the corresponding terminal while the engine is running. Unreliable contact will be determined by a change in the nature of the engine. Restore contact reliability by replacing or cleaning the appropriate connector. Keep in mind that in some cases you will have to change entire harnesses.
If, as a result of preliminary checks, you did not find the cause of unstable engine operation, the car should be driven to a service station for a more thorough diagnosis using special equipment.
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