In this article, we will look at possible faults that may occur during the operation of the vehicle.
The engine will not start
Starting the engine with a fuel injection system is the same at any temperature of the ambient air and the fluid in the engine cooling system.
To start the engine, you only need to switch on the starter without pressing the accelerator pedal, and the system will adjust itself to the necessary parameters of fuel supply and ignition advance.
If the engine fails to start after three attempts, then:
We open the bonnet by pulling the release handle towards ourselves.
We measure the oil level with the dipstick.
In the K4M engine, the oil level must be between the upper and lower limits of the shaded area.
In the F4R engine — between the lower and upper marks on the dipstick.
We check the coolant level.
It must be between the MIN and MAX marks on the expansion tank.
We inspect the engine.
We pay attention to traces of petrol, oil and coolant.
We check the integrity of the electrical wiring. We check the seating of the wiring harness connectors in the ignition coil sockets.
After inspecting the engine and systems, we try to start the engine once more.
If the engine does not start on the first attempt, we press the accelerator pedal to the floor and operate the starter for two to three seconds.
In this mode, the cylinders are purged, fuel is not supplied through the injectors and no voltage is applied to the spark plugs.
After purging the cylinders, we try to start the engine in the normal mode, without pressing the accelerator pedal.
If the engine still does not start, it means:
- the fuel system is not working;
- the ignition system is not working;
- the starting system is not working.
Starting faults
The starter does not engage. The cause may be a disturbance of the contacts and connections.
An open circuit or short circuit in the starter engagement circuits, a fault in the pull-in relay.
If clicks are heard when the starter is engaged, the cause is a discharged battery, oxidised or weak contacts on the battery or starter.
The cause may also be a fault in the hold-in winding of the pull-in relay.
If the starter engages, but the armature either does not rotate or rotates slowly.
Cause — discharged battery, disturbed contact connections, burnt contacts of the pull-in relay, dirty commutator or worn brushes, inter-turn or short circuit in the starter windings.
If the starter engages, its armature rotates, but the flywheel is stationary.
The cause may be a loosening of the starter mounting to the clutch housing, damage to the teeth of the flywheel or drive pinion, slipping of the drive freewheel clutch, breakage of the lever, drive ring or buffer spring of the starter drive.
If the starter does not disengage after the engine starts.
Cause — fault in the starter freewheel clutch, welding of the pull-in relay contacts. If such a fault occurs, the engine must be stopped immediately.
Checking the ignition system
The ignition system on the vehicle is a microprocessor (MPSZ) high-energy system.
In the ignition coils, the voltage is transformed to approximately 40,000 volts.
We check the integrity and seating of the ignition coils on the spark plugs.
We check the ignition coils. To do this, we remove the coil of the first cylinder.
We install a verified spark plug in the coil and press the spark plug against the metal part of the engine.
An assistant turns the crankshaft with the starter.
A strong spark must jump between the spark plug electrodes.
If there is no spark, the ignition coil must be replaced. We check the remaining coils in the same way.
During this check, there must be reliable contact of the spark plug with earth, otherwise the engine management unit or the high-voltage circuit of the ignition coil may be damaged.
Such a check must be carried out for no more than five seconds, so as not to damage the exhaust catalytic converter when unburnt fuel from the engine cylinders enters it.
If after this check the engine does not start, the serviceability of the engine management system must be checked.
Checking the engine fuel system
The main criterion for the serviceability of the fuel system is the fuel pressure in the rail.
It is recommended to make sure the air filter is clean before this check.
We check the fuel pressure using a pressure gauge with adapters.
With the engine running at idle, the pressure in the rail must be approximately 2.7 kgf/cm².
The following causes of pressure reduction are possible:
Fault in the fuel pump.
Clogging of the mesh filter of the fuel module.
The serviceability of the pump and the cleanliness of the filter can only be checked after removing the fuel module.
Faults in the fuel injection system
The vehicles use a distributed fuel injection system.
Injection is called distributed because the fuel is injected into each cylinder by a separate injector.
The fuel injection system makes it possible to reduce the toxicity of exhaust gases while improving the driving qualities and fuel economy of the vehicle.
In the fuel injection system of the engine with feedback in the exhaust system, an exhaust catalytic converter and two oxygen concentration sensors are installed, which provide the feedback.
The sensors monitor the oxygen content in the exhaust gases, and the electronic control unit, based on their signals, maintains such an air-fuel ratio at which the catalytic converter works most efficiently.
Before removing any components of the injection control system, disconnect the wire from the negative terminal of the battery.
Disconnect the battery only with the ignition switched off.
Do not start the engine if the wire terminals on the battery are poorly tightened.
Never disconnect the battery from the vehicle's on-board network while the engine is running.
When charging, disconnect the battery from the vehicle's on-board network.
Do not allow the electronic control unit (ECU) to heat above 65 °C in the operating state and above 80 °C in the non-operating state (for example, in a drying chamber after painting).
If this temperature is exceeded, the ECU must be removed from the vehicle.
Do not disconnect from the ECU or connect to it the wiring harness connectors with the ignition switched on.
Before carrying out electric arc welding on the vehicle, disconnect the wires from the battery and the wire connectors from the ECU.
Perform all voltage measurements with a digital voltmeter whose internal resistance is at least 10 MΩ.
The electronic components used in the injection system are designed for very low voltage, so they can easily be damaged by electrostatic discharge.
To prevent damage to the ECU by electrostatic discharge:
- do not touch with your hands the ECU plugs or the electronic components on its boards;
- when working with the programmable read-only memory (PROM) of the control unit, do not touch the terminals of the microcircuit.
When working in rainy weather, do not allow water to enter the electronic components of the fuel injection system.
Carry out the check of the injection system in the following order:
- check the connection to earth of the engine and the battery;
- check the pressure regulator, the fuel filter and the fuel pump;
- check the fuses and relays for switching on the elements of the injection system;
- check the reliability of the contacts of the connectors with the wires of the elements of the injection system;
- check the sensors of the injection system.
The vast majority of faults in the fuel injection system are caused by the failure of the following sensors:
- crankshaft position — complete failure of the injection system, the engine will not start;
- throttle position — loss of power, jerking and hesitation during acceleration, unstable idle operation;
- coolant temperature — difficulty starting in frost. The engine has to be warmed up while maintaining the speed with the accelerator pedal. In case of overheating, the power drops significantly, knocking appears;
- intake air temperature sensor — if the sensor fails, difficulty starting in frost, the engine has to be warmed up while maintaining the speed with the accelerator pedal; in case of overheating, the engine power decreases, knocking appears;
- absolute pressure (vacuum) sensor in the intake pipe — increased fuel consumption, significant deterioration in dynamics, jerking and hesitation, problems with starting the engine;
- knock sensor — the engine is very sensitive to the quality of petrol, increased tendency to knocking;
control oxygen concentration sensor (lambda probe) — increased fuel consumption, reduced engine power, unstable idle operation.
Possible damage to the exhaust catalytic converter;
- diagnostic oxygen concentration sensor. Possible damage to the exhaust catalytic converter;
- vehicle speed sensor
- possible deterioration in the dynamic qualities of the vehicle in modes using maximum power (intensive acceleration);
Idle speed has disappeared
To determine the causes of this fault, special diagnostic equipment is required, so in this case contact a maintenance station specialising in the repair of vehicles with injection engines.
Most often this fault is caused by the failure of the idle speed control valve or by air being drawn in through the loose connections of the throttle body hoses.
If it has not been possible to restore the idle speed by replacing the control valve and tightening the hose clamps, contact specialists.
Misfiring in engine operation
With misfiring, the engine runs unevenly at idle, does not develop sufficient power, and consumes more petrol.
Misfiring, as a rule, is explained by a fault in the injectors or the electric fuel pump; the spark plug of one of the cylinders, by air being drawn into one of the cylinders. It is necessary to find the fault and, if possible, rectify it.
Start the engine and leave it running at idle. Go to the exhaust pipe and listen to the sound of the exhaust.
You can hold your hand to the cut of the exhaust pipe — this way the misfiring is felt better. The sound must be even, "soft", of one tone.
Bangs from the exhaust pipe at regular intervals indicate that one cylinder is not working due to the failure of the spark plug, the absence of a spark on it, the failure of an injector, strong air being drawn into one cylinder or a significant reduction in compression in it.
Bangs at irregular intervals arise due to contamination of the injector nozzles, severe wear or contamination of the spark plugs.
If the bangs occur at unequal intervals, you can try to replace the whole set of spark plugs yourself regardless of the mileage and appearance, however it is better to do this after contacting a car service for diagnostics and repair of the engine management system.
If the bangs are irregular, stop the engine and open the bonnet.
Check the condition of the ignition system wiring harness and the fastening of the wire connectors on the ignition coils. If there is damage to the wires, replace the whole ignition system wiring harness.
Unscrew the spark plugs. Carefully inspect the spark plugs and compare their appearance with the photographs given in the article below.
If all the spark plugs look serviceable, refit the spark plugs and coils and connect the wiring harness connectors to them.
Disconnect the wiring harness connector from the coil of the 1st cylinder. Start the engine.
If the misfiring of the engine has not intensified, replace the spark plug in the 1st cylinder with a known serviceable one.
Fit the high-voltage lead and start the engine.
If the misfiring has intensified, repeat the procedure successively with all cylinders to identify the faulty spark plug.
If, as a result of the measures taken, the misfiring of the engine has not been eliminated, check the compression in each of the cylinders.
- Normal compression — more than 1.0 MPa (10 kgf/cm²); a difference in compression values in the cylinders of more than 0.2 MPa (2 kgf/cm²) indicates the need for engine repair.
Diagnostics by the appearance of the spark plugs
Normal spark plug
Brownish or greyish-yellowish colour and slight wear of the electrodes.
Correspondence of the heat value of the spark plug for the engine and the working conditions.
Soot deposit
Deposit of dry soot indicates a rich mixture or late ignition.
Causes misfiring, difficult engine starting and unstable engine operation.
Oily electrodes and insulator of the spark plug
Cause — oil entering the combustion chamber.
Oil enters the combustion chamber through the valve guides or through the piston rings.
Causes difficult starting, misfiring in the operation of the cylinder and jerking of the running engine.
Advice. Carry out the necessary repair of the cylinder head and the piston group of the engine. Replace the spark plugs.
Metal-containing deposit
Deposit on the skirt of the insulator of iron oxides of brownish-red colour from anti-knock iron-containing additives (ferrocenes) to petrol.
They are deposited in an even, dense layer.
During engine operation with a large load with high temperature and pressure in the combustion chamber, the oxides are converted into conductive tracks of pure iron, short-circuiting the centre electrode to earth.
This causes misfiring, a drop in engine power.
This can cause damage to the exhaust catalytic converter.
The deposit is practically not removed mechanically and does not burn off when driving at high speed.
If there is no possibility of immediately replacing with new spark plugs, we place the spark plug in a rust converter, after this we clean the spark plug with a metal brush, wash it with water, and then with petrol.
Melted electrodes
Early ignition.
The insulator is white, but may be contaminated due to spark misfiring and deposits from the combustion chamber entering it. May lead to damage to the engine.
It is necessary to check the correspondence of the spark plug type, the cleanliness of the injector nozzles and the fuel filter, the operation of the cooling and lubrication systems.
Insulator with cracks or chips.
The damage is caused by knocking. May lead to damage to the piston.
Occurs in case of a fault in the knock sensor. Make sure that the petrol meets the requirements.
Mechanical damage to the spark plug
Damage may be caused by foreign objects that have entered the combustion chamber, and in the case of using a spark plug with a long skirt, its electrodes may catch the piston.
We remove the foreign object and replace the spark plug.
The vehicle moves with jerking
In relation to the vehicle, a jerk is a short-term spontaneous change in the crankshaft speed of the engine, regardless of the position of the accelerator pedal.
In everyday operation, as a rule, series of jerks occur.
The limiting case of a jerk — the hesitation — is a perceptible delay in the response of the engine to pressing the accelerator pedal.
Conditionally, three types of jerks can be distinguished:
- at the moment of starting off;
- during acceleration;
- during steady movement, i.e. with a constant position of the accelerator pedal.
To determine the causes of jerking during the movement of a vehicle with an injection engine, special diagnostic equipment is required, so in this case we recommend contacting a service specialising in the repair of fuel injection systems.
However, as practice shows, in most cases jerking is caused by insufficient fuel pressure in the fuel rail, by faults in the throttle position sensor.
With certain skills, the cause of jerking can be determined independently.
Jerk at the moment of starting off
At the moment of starting off, the limiting case of a jerk — the hesitation — most often occurs.
The most unpleasant sensations are connected precisely with the delay in the response of the engine to pressing the accelerator pedal.
Sometimes the engine even stalls at this.
The jerk occurs at the moment of the beginning of the opening of the throttle, when, on the signal of the throttle position sensor, the ECU determines the moment of transition from the idle mode to the load mode and must increase the amount of fuel supplied through the injectors.
With insufficient pressure in the fuel line (even with an increase in the injection duration), there is not enough fuel for a smooth pulling away.
Jerking during acceleration
The cause of jerking during acceleration can be, as in the previous case, insufficient fuel pressure in the fuel line.
The engine electronic control unit, having received from the throttle position sensor the signal about the intensive opening of the throttle by a large angle, strives to increase the fuel supply to the maximum, but due to the reduced fuel pressure is unable to do this.
The causes of this phenomenon and the method of checking are the same as in the previous case.
Jerking during movement
Such jerking is most often caused by a fault in the ignition system.
Diagnostics and repair are necessary. On the road, you can try to do the following yourself:
- carefully inspect the engine compartment.
Switch off the ignition and check the reliability of the fastening of the wiring harness connectors to the ignition coils.
Start the engine and listen to its operation: the crackle when the high voltage breaks down "to earth" is weak but distinct. In complete darkness, the spark during breakdown is clearly visible;
- replace the spark plugs regardless of their condition and mileage.
Pay attention to the condition of the spark plugs: if it is abnormal, it may be necessary to repair the engine or its systems.
A specific cause of jerking during steady movement of a vehicle with an injection engine may be the failure of the throttle position sensor.
Additional symptoms confirming the fault of this sensor are:
- uneven engine operation at idle;
- reduction in maximum engine power.
The sensor is non-demountable and therefore not repairable. If a fault in the sensor is detected, it is replaced as a unit.
The car accelerates poorly
There are many causes of deterioration in dynamics, the main ones can be defined as follows.
Engine fault: reduction in compression in one or more cylinders, additional air being drawn into the engine intake tract.
Coking of the exhaust system or damage to the exhaust catalytic converter.
Fuel system fault: clogging of the injectors and the fuel filter, of the fuel supply system hoses.
Insufficient delivery of the fuel pump. Use of low-quality fuel.
Ignition system fault: failure of the spark plug, breakdown of the high-voltage circuit of the system.
Engine management system fault: failure of the system sensors.
If any sensor fails, the electronic control unit switches to operation according to a backup programme, which allows reaching the garage or car service, but the power and economic characteristics of the engine are reduced.
Clutch slipping due to wear or disturbed adjustment.
Brake system fault: braking of one or more wheels during movement, incorrect adjustment of the parking brake.
Insufficient air pressure in the tyres.
Overloading of the vehicle.
The complete diagnostics of the vehicle must be carried out by highly qualified masters using special diagnostic equipment, so contact a car service.
You can carry out the following work yourself:
Check and bring the air pressure in the tyres to the norm.
Check the operation of the service brake system and the parking brake. It is not necessary to remove the wheels for this.
Find a level section of road and, in dry, windless weather, carry out a run to determine the coasting of the vehicle.
The vehicle must be fully fuelled, only the driver in the cabin.
Accelerate the vehicle to 50 km/h, even out the speed, then disengage the gear and move by inertia until it comes to a complete stop.
Carry out another run in the opposite direction. The coasting distance must be about 500 m.
Check the operation of the ignition system as described above.
Check the operation of the clutch of a vehicle with a manual gearbox.
The initial check is carried out on a level area free of obstacles.
Set an increased idle speed with the accelerator pedal — approximately 1500 min⁻¹.
Brake the vehicle with the parking brake.
Depress the clutch and engage first gear. Then begin to release the clutch pedal smoothly.
If the engine stalls, the clutch is serviceable and does not slip.
If the engine does not stall, the clutch is worn, it must be replaced or the drive adjusted.
Check the serviceability of the engine management system.
The engine stalled during movement
Sooner or later, every driver may find himself in a situation where the vehicle, which a few moments ago obeyed all commands, suddenly stops responding to pressing the accelerator pedal, and red lights come on on the instrument panel.
The engine has stopped working, the vehicle is losing speed. What to do in such a situation?
The most important thing — do not get nervous! Switch on the hazard warning lights, depress the clutch pedal and, using the inertia of the vehicle, try to move carefully to the edge of the carriageway and stop as far to the right as possible at the roadside, and if possible, outside the carriageway.
Bear in mind that with the engine not running, the effectiveness of the vehicle's brake system is reduced, so braking may require greater effort on the brake pedal.
Apply the parking brake. If the vehicle has stopped on a slope, use wheel chocks.
In difficult traffic conditions and on country roads, put out the warning triangle, as provided for by the "Highway Code". Now it is necessary to find out and rectify the fault that has arisen.
There are two main causes:
- the ignition system is not working;
- the fuel system is not working.
To begin with, determine whether there is petrol in the tank. Switch on the ignition and look at the fuel level gauge.
If the yellow reserve fuel warning lamp is not on and the gauge needle shows the presence of fuel, it can be assumed that there is petrol in the tank.
Open the bonnet and carefully inspect the engine compartment.
Pay attention to the integrity of all units. Check whether all the wires are in place, whether there are any torn, burnt, with damaged insulation.
Inspect the petrol hoses, the engine fuel line and the fuel filter — whether there are traces of petrol.
If petrol is leaking, in no case start the engine until the fault is completely rectified!
Inspect the cooling system expansion tank — whether the coolant has leaked out.
Also check the oil level in the engine sump.
If everything is in order, proceed to the check of the ignition and fuel systems described earlier, but first check the condition of the timing mechanism drive belt.
With a broken belt, the engine will not start without visible causes.
The oil pressure has dropped
In the vehicle's instrument cluster there is an oil pressure warning lamp for the engine.
For reliable operation of the engine, it is necessary that a sufficiently high pressure is constantly ensured in the lubrication system.
If, with the engine running, the oil pressure warning lamp comes on and continues to burn at increased speed, this is an alarming sign.
It is necessary to stop movement immediately, stop the engine and find out the cause.
Further operation of the engine with reduced oil pressure can lead to a serious breakdown of it and large financial costs for repair.
Open the bonnet. Do not rush to check the oil level in the engine immediately, let it drain into the oil sump, this will take two or three minutes.
During this time, carefully inspect the engine, find out whether there are fresh traces of oil on it.
Look under the front part of the vehicle — whether the engine oil sump is pierced, whether there is a leak there.
If an oil leak from a pierced oil sump is detected, try to patch it temporarily on the spot.
For this, you can use an inner tube, a piece of rubber, a rag, a wooden plug, etc.
A good result can be given by the use of modern repair materials such as "cold welding", available for sale in car shops.
Pay special attention to the oil filter.
Oil may leak from under the rubber gasket of the filter if it is damaged or the filter is poorly secured.
If oil leaks from under the oil filter, sometimes it is enough to tighten it slightly clockwise.
Be careful: you can burn yourself on the hot parts of the engine, so put on gloves and long-sleeved clothing.
If the oil level is below the lower mark of the scale, top up the oil to the norm.
Start the engine.
If, with a normal level, the oil pressure warning lamp has gone out, movement can be continued.
If the lamp does not go out, check the serviceability of the oil pressure sensor.
It is installed on the side of the cylinder block facing the cooling system radiator.
Unscrew the standard oil pressure sensor and install a mechanical pressure gauge in its place.
If, at normal idle speed, the pressure is more than 0.06 MPa (0.65 kgf/cm²) and increases with increasing speed, the sensor or its electrical circuit is faulty.
If you do not have a pressure gauge, all that remains is to check the reliability of the contact in the connector with the sensor wires or replace the sensor with a known serviceable one.
If, after rectifying all visible causes, the oil pressure in the engine is insufficient (the oil pressure warning lamp is on), carry out diagnostics and repair of the engine.
Engine overheating
Disturbances in the operation of the cooling system can lead to engine overheating.
If the moment of engine overheating is missed, the following may occur:
- breakdown of the cylinder head gasket;
- warping of the head.
In the instrument cluster there are the coolant temperature gauge "А" and the engine overheating warning lamp "Б".
If the engine overheats, the gauge scale is completely shaded (at normal temperature, the four lower divisions of the scale are shaded) and the warning lamp comes on.
Checking the cooling system
At the first signs of overheating, if the gauge scale is completely shaded, but no vapours are escaping from under the bonnet, the maximum heater mode of the cabin must be switched on to reduce the coolant temperature.
The engine must not be stopped immediately if there is no fluid leak from a burst hose or if another leak point has formed.
Stop the engine.
Open the bonnet and determine the place of the fluid leak.
Look under the floor mats of the front passenger and determine whether there is fluid leaking from the heater radiator under them.
If there is no antifreeze during the journey, you can simply top up with water. Cold water must not be added to an overheated engine.
The engine may overheat in the case of a fault in the thermostat.
To check the thermostat, with the engine warm, check by touch the temperature of the lower hose connecting the radiator to the engine.
If the lower hose is cold, the thermostat is faulty, there is no circulation of fluid through the radiator.
Often the cause of engine overheating is the failure of the fan electric motor.
Start the engine, monitor the temperature and pay attention to whether the cooling system fan switches on when the engine overheats.
If it does not switch on, the cause may be a fault in the additional resistor, a blown fuse, a fault in the switch-on relay, oxidation of the contacts in the wiring harness connector or a burnt-out electric motor.
Replace fuse "А" in the engine compartment fuse and relay box.
If the fan has not started working after replacing the fuse, we replace relays "Б" and "В".
If after these manipulations the electric fan has not started working, we check the fan electric motor.
To do this, we connect the wires directly to the electric motor and to the battery.
If the electric motor has started working, it means that the electrical wiring is faulty.
A great role in ensuring the optimal temperature regime is played by the valve of the expansion tank cap. It maintains an excess pressure in the system of at least 0.15 MPa (1.5 kgf/cm²).
At this, the boiling point of water rises to 120 °С, and of antifreeze to 130 °С.
If the valve jams in the closed position during overheating, a significant excess of the excess pressure occurs [more than 0.2 MPa (2 kgf/cm²)], which can lead to rupture of the expansion tank or detachment of one of the hoses.
Once a year, wash the radiator cells with a high-pressure water jet (at a special car wash), directing the jet first against the oncoming air flow, and then in its direction to remove dirt, stuck insects and road debris from the radiator surface. At this, the radiator efficiency is partially restored.
The battery is not charging
The vehicle has two sources of current — the battery and the alternator. The battery is used when starting the engine and to supply 12 V electrical current to the starter and other consumers when the engine is not running.
When the engine is running, the main source of current — the alternator — supplies electrical current to all consumers, including the ignition system, and charges the battery.
If the red battery charge lamp is on on the instrument panel, it means that current is not coming from the alternator to the on-board network and the battery's energy reserve is being consumed.
This reserve is limited and depends on the capacity.
If the battery was fully charged, you can reach the garage even without the alternator, but it is better to try to rectify the fault on the spot.
Checking the electrical equipment
We check whether the auxiliary drive belt is broken. If the belt is broken, we replace it.
If the belt is intact, we check and, if necessary, adjust its tension.
We press on the belt run with the thumb; if the distance between the centres of the pulleys is 180–400 mm, the deflection must be approximately 6 mm, and if the distance is 300–400 mm, the deflection must be 13 mm.
If, after checking the belt tension, the warning lamp still burns, we check the wires connected to the "+" terminal of the battery.
We check the wires connected to the "−" terminal of the battery.
We check the wires connected to the starter.
We check the wires connected to the alternator.
If, after the measures taken, the charge lamp still burns, it means that the fault is in the alternator itself.
Knocking in the engine
If it seems to you that during the operation of the engine sounds have appeared that were not there before, immediately make sure that everything is in order with the engine.
Most often, knocking in the engine is associated with serious faults, for the diagnosis and rectification of which the engine will have to be dismantled in the conditions of a service or garage.
You can try to determine the cause of the knocking yourself, in order to decide whether to go to the car service under your own power or on a tow truck.
If you have the slightest doubt about the results of the self-diagnosis, get out the tow rope.
A serious repair of a damaged engine will cost more than the services of a tow truck.
Knocking of the main bearings — very dangerous; stop the engine immediately, you will have to go to the car service or garage on a tow truck. Low-tone knocking.
It is heard in the lower part of the sump, noticeably intensifies under load and with increasing speed.
Often its appearance is accompanied by a drop in oil pressure (the oil pressure warning lamp burns almost constantly).
Knocking of the connecting rod bearings — very dangerous; stop the engine immediately, you will have to go to the car service or garage on a tow truck.
The sound is rhythmic, ringing, metallic, of medium tone. It increases significantly with increasing load and completely disappears when the spark plug is switched off.
Knocking of the piston pins — dangerous; without loading the engine, you can reach the car service or garage yourself.
Rhythmic, high-tone with a sharp metallic tinge, it is heard in all operating modes of the engine and intensifies with increasing load on the engine.
It completely disappears when the spark plug is switched off.
Knocking of worn pistons and cylinders — not dangerous; without loading the engine heavily, you can reach the car service or garage yourself.
A sound reminiscent of the knocking of clay crockery. It is especially well heard on a cold engine, and decreases or disappears as it warms up.
Knocking of the valves — not dangerous; you can reach the car service or garage yourself. Metallic knocking against the background of a general dull noise.
It is well heard at low and medium crankshaft speed from the side of the cylinder head above the places where the valves are located.
Knocking of detonation — dangerous; however, avoiding heavy loading of the engine, you can reach the car service or garage yourself.
Ringing metallic knocking, arising, as a rule, during acceleration of the vehicle.
Cause — fault in the knock sensor, use of low-octane fuel, overloading of the engine when engaging a higher gear too early, significant carbon formation in the combustion chambers.
It is necessary to choose the gear correctly depending on the traffic conditions, to fill up with petrol of the octane number recommended by the vehicle manufacturer, to check the knock sensor, to use a special fuel additive to remove carbon deposits on the valves and in the combustion chambers.
Knocking in the suspension and transmission
When extraneous knocking appears in the suspension of a moving vehicle, it is necessary to establish their source immediately, regardless of whether it is a constant knocking or one that appears only when driving over irregularities.
Check the suspension.
It is better to check the condition of the suspension by placing the vehicle on a ramp, inspection pit or lift, and if there is no such possibility, you can carry out this work, although with less convenience, on a free level area. In any case, you will need an assistant.
It is quite difficult to diagnose the serviceability of the transmission units by the noises they emit.
If you have not managed to determine the source of the noise precisely, contact a qualified specialist.
Repair or replace the failed suspension units.
The cause of knocking from below may be faults not only in the suspension, but also in the vehicle's steering.
The condition of the steering largely affects not only the convenience of driving the vehicle, but also the safety of movement.
The cause of knocking and vibration on the steering wheel may be the faulty condition of the ball joints of the steering rods and the steering mechanism, of the vehicle's wheels. Check the steering.
A possible cause of vibration and impacts on the steering wheel when driving at a speed of more than 70–80 km/h may be the imbalance of the front wheels.
Contact a car service or a tyre fitting point to check the balancing of the front wheels.
If impacts and vibration on the steering wheel appear at the moment of pressing the brake pedal, replacement of the brake pads, repair or replacement of the front brake discs is necessary.
