Idle mode, abbreviated as XX mode, is a state of engine operation in which the mechanical energy of the motor is not transmitted to the gearbox. Idling occurs when the clutch pedal is pressed if the gearbox is mechanical, as well as when the gearshift lever is in neutral.
You should pay attention to the engine idling. It often happens that the engine vibrates strongly at idle.
Engine vibrations at idle:
- diesel engine vibrates at idle;
- The gasoline engine vibrates when running on gas if a 4th generation or earlier generation gas system is installed;
- The gasoline power unit vibrates when running on gasoline.
Idle performance can be very different when the engine is cold or hot.
Engine vibration - is this normal?
Every motorist knows his car and literally feels and hears by touch whether everything is in order with it.
Vibrations are no exception - if you suddenly begin to feel the steering wheel, gear lever, pedals and the entire car rattling, and this was not the case before, this is already an alarming signal. Such rattling may indicate serious damage to the engine, in particular in its cylinder-piston group, and this already threatens costly repairs. Vibrations at low speeds are normal within reasonable limits, since the motor can enter into slight resonance at a low frequency of its own vibrations. This is most often observed at idle, during cold starts or stopping the engine.
Vibration at idle
Vibrations are the rattling sounds produced by the engine and felt by the driver when he holds the steering wheel.
If there are problems with the engine, the rattling from barely perceptible becomes very strong and unpleasant.
Signs
The main symptoms of this problem include:
- increased vibration of the steering wheel, which can be transmitted to the engine body;
- engine popping;
- engine jerks and failures;
- The tachometer readings exceed the permissible values for the car.
It will also be useful for you to know why the car shakes during acceleration and at high speed.
Causes
The main causes of engine vibrations include:
- engine tripping (uneven operation of the pistons or failure of one of them);
- incorrect motor mounting;
- faulty engine mounts;
- the crankshaft is unbalanced;
- the fuel system is dirty;
- improper fastening of other units;
- ignition system malfunction.
- One of the common mistakes associated with engine mounts is installing mounts from different materials.
The above reasons are valid for gasoline cars.
The reasons why the vibrations of a diesel engine have increased, due to the difference in design and operation from a gasoline engine, are slightly different:
- malfunction of the cylinder-piston group or gas distribution mechanism as a whole or in a separate cylinder;
- compression variation in cylinders;
- malfunction of the high pressure fuel pump, diesel injectors or timing belt teeth;
- incorrect injection advance angle.
Why is low engine idle dangerous?
No less a problem is reducing idle speed.
Low speeds can lead to the following consequences:
- fuel detonation in the cylinders does not occur completely;
- oil dilution;
- washing off the lubricant;
- coking of the motor.
It is also worth noting that at low idle speeds the car will stall, as it will not have enough revolutions to maintain operation. This, in turn, will increase the load on the ignition system, increasing wear on the car and reducing its service life.
Diagnostics
To carry out diagnostics, you should pay attention to the following points:
- check the injector/carburetor;
- take readings from the tachometer and pressure sensor and compare them with normal values;
- check the fastening of the motor and other components;
- run computer diagnostics of the car (if there are appropriate electronics on board).
Separately, it is worth mentioning the process of checking engine mounts, since their incorrect installation quite often causes problems, although they are easily diagnosed and corrected.
Important! Since visible problems may hide other, more serious ones, if any problems occur, you should contact a car service center.
Checking the airbags is carried out as follows: one person sits behind the wheel, opens the hood and drives back and forth in place, the second person watches the engine at this moment - it should tilt evenly in all directions. If the engine rolls a little more in one direction, then the cushion on that side should be replaced.
What measures to take in case of strong vibration
When faced with strong vibrations, you can begin to combat the problem.
Engine adjustment
Adjusting the motor, first of all, includes checking the fastenings of the parts, as well as their condition. Having ensured that they are in good working order and correctly secured, it is necessary to calibrate their joint work.
The best way to do this is to check the factory settings in the instructions and reset all settings to them. Tuning includes not only tuning the operation of the engine itself, but also related systems - fuel supply, ignition, and so on.
If parts have been replaced, it is necessary to ensure that the parts in weight and material match those that were replaced - otherwise imbalance will occur.
Did you know? If the crankshaft is too heavy, it is lightened by cutting out holes, thereby knocking off the extra grams.
Correct installation of the timing belt
Another important element in solving the problem is installing the timing belt. The belt is responsible for the connection between the crankshaft and the camshaft, and its incorrect installation will inevitably lead to disruption of the gas distribution system.
The belt is replaced as follows:
- the protective belt cover is unscrewed;
- disconnects from the sensor;
- checking the coincidence of the marks on the camshaft gear (or shafts, if there are several of them), the gas distribution mechanism drive, the flywheel, the crankshaft - this will ensure the correct valve timing;
- the old belt is removed;
- a new belt is put on: first on the crankshaft pulley, then on the camshaft gear and pump;
- two revolutions of the crankshaft are carried out, after which the marks are checked - if the belt is installed correctly, they will coincide.
Causes of engine vibrations in different operating modes
Vibration can be observed both constantly, regardless of engine speed and warming up, and during certain operating modes - at idle, when starting cold or hot, at low or high speeds while driving.
Low speeds during idling of the internal combustion engine often lead to slight vibration of the entire car, including the steering wheel. While there is no clutch and the engine does not transmit power to the wheels, it operates at a minimum speed of 800-1000 rpm. If the tachometer shows lower or higher values, this is already a reason to contact a service station, but this is also an average indicator, which may differ in both directions depending on the make and model of the car.
Resonance often occurs when the engine is started cold, and when it reaches normal speed, the vibration goes away after warming up for 3-5 minutes. If the engine continues to vibrate at idle after starting or while driving, i.e. when hot, and the vibrations themselves become more and more noticeable, this already indicates a malfunction. Among them, car service experts identify five main ones:
- Incorrect motor mounting. This problem often occurs when the car is repaired unprofessionally and the engine is disassembled. Lack of balancing and improper mounting can all lead to vibrations when starting cold or hot, when idling and while the vehicle is moving.
- Faulty engine mounts. This problem can arise by itself under extreme operating conditions of the car or be a consequence of the previous point - improper disassembly and reassembly of the engine, violation of the car repair technology, etc. With this type of malfunction, a cold engine vibrates especially noticeably. This is due to the fact that the polymer elements of the motor mounts lose their elasticity when cooled and do not fully perform their damping functions. After the engine warms up, the vibration stops due to the restoration of the shock-absorbing properties of the gaskets.
- Unbalanced crankshaft. A loose crankshaft leads to pendulum oscillations of the engine, which resonates with the small vibrations of the car, creating a powerful vibration that is noticeable in the cabin. Vibration with an unbalanced crankshaft can be observed both at idle when starting cold or hot, and while the car is moving.
- Vibrations when starting the engine when cold can also be observed with faulty fuel injectors. Simply put, an insufficient amount of fuel enters the combustion chamber, which prevents the combustion of the air-fuel mixture and leads to triple combustion.
- Engine tripping. This is the most common reason for engine vibration at idle. In addition to malfunctions in the fuel system, problems in the cylinder-piston group itself often lead to tripping, incl. wear of its elements and friction surfaces. Uneven operation of the cylinders introduces the engine into vibration resonance precisely at low idle speeds. While driving, when the engine is running under load, this effect is not so noticeable.
Jerking and jerking of the engine, leading to general vibration of the machine, appears as a result of uneven distribution of the load on the crankshaft. Even if you press the gas pedal at idle, thereby compensating for the drop in power and speed due to an inactive cylinder, the driver will still feel a noticeable vibration. It is transmitted to the steering wheel, through which drivers most often detect suspicious rattling, and it can also be transmitted to the hood, which literally begins to drum.
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Speed
This is 800-1000 rpm. If the number of crankshaft revolutions is lower, the engine will begin to stall; with a higher number, fuel consumption will increase and engine parts will wear out faster. It is worth noting here that in the cold season, slight vibration after start is a normal phenomenon, which disappears after 5 minutes as the power plant warms up. If the engine shaking does not disappear, it is necessary to consider the reasons for its occurrence.
How to determine the cause of vibration and eliminate it?
The first step is to determine the root cause of vibration and then boldly eliminate it.
- Check the fuel system and spark plug operation.
- If the engine has recently been repaired and disassembled, check the quality of its fastening at a service station.
- Make sure the support pads are in good condition.
- The runout of an unbalanced crankshaft can be either an independent cause of vibration or a consequence of malfunctions in the CPG.
Troubleshooting is the most common cause of vibration in an engine at idle. This malfunction can be detected at a service station. However, you can notice the signs of tripling yourself.
- More frequent misfires.
- Frequent popping sounds from the exhaust pipe.
- Significant reduction in engine power.
- Vibrations from the engine compartment at idle, transmitted to the steering wheel.
- Darkening of the spark plug in an idle cylinder.
- Long acceleration times and jerks when accelerating.
- Increased fuel consumption.
It is necessary to eliminate such a malfunction as quickly as possible, since this exponentially leads to aggravation of the problem, further breaking the pistons, cylinder cups and crankshaft. During triplication, unburned fuel washes away the lubricant in the engine cylinders, increasing the coefficient of friction and accelerating wear of the rubbing surfaces of the cylinder-piston group.
Engine mounting
Strong vibration of the engine at idle speed can be caused by poor fastening of the power plant to the body. In some cases, it is possible to identify breakdowns of the protective cushion through which the motor is attached. It is advisable to carry out diagnostics together with an assistant, who will sequentially switch gears in the gearbox. An observer looking under the hood will identify which gears are causing problems.
Even after replacing the airbags, the shaking does not always leave the car. This is due to the need to properly configure and adjust the fasteners.
Failure can occur for any of the four supports (rear, front, bottom or top). However, practice shows that the most vulnerable is the front support. It is subject to increased static and dynamic load. As soon as one of the pillows breaks, then if no measures are taken, the rest will quickly break .
For novice drivers, vibration in the steering wheel at idle is not always obvious, so we recommend periodically undergoing diagnostics in specialized workshops or from experienced technicians. Otherwise, trouble cannot be avoided. If you decide to look for the cause yourself, then you need to use the method of exceptions, moving from simple to complex causes.
What causes tripling?
The problem may be hidden in a non-working spark plug or a violation of the insulation of the electrical wiring supplying it. This can be determined independently by visual inspection. Masters carry out more detailed diagnostics of the ignition system by transferring the spark plug's power supply to ground. If the engine stalls, the cylinder is working properly; if it does not stall, it is not working.
If all cylinders are working, i.e. in them the air-fuel mixture ignites, then the cause of the tripping and accompanying engine vibration is the wear of the cylinder-piston group. This may be due to scratches, chips, scuffs and other damage to the mirror of the cylinder cups and piston, as well as if the integrity of the sealing rings is damaged.
As a result of CPG wear, a significant decrease in compression in the cylinders is observed. This leads to jerky operation of the engine with the appearance of vibration, which intensifies due to resonance at idle.
Through scratches and chips on the friction surfaces of the CPG, engine oil penetrates into the combustion chamber, and fuel and exhaust gases penetrate in the opposite direction. This dramatically worsens the rolling of the pistons and leads to unbalance of the crankshaft. Such loose operation of the entire cylinder-piston group, including the crankshaft, causes strong resonating vibrations at idle speeds during cold starts and even while the car is moving at low speeds.
Engine vibration may go away briefly after changing the engine oil, but this is a temporary effect. Without eliminating the root cause, the oil in the crankcase will again acquire negative properties that disrupt the normal operation of the cylinder-piston group. If scratches and chips remain on the rubbing surfaces of the cylinder and piston, exhaust gases and fuel will again enter the crankcase through them.
This problem can be eliminated not only by replacing the entire CPG at a service station, but also with the help of special tribological reducing compounds that are added to the engine oil.
What else could cause this phenomenon?
If, after examining the operation of the fuel supply channels, ignition system, support cushions and understanding that all this is functioning normally, the engine continues to vibrate in neutral speed mode, then the reason is something else.
One possible option is a faulty gearbox. To determine the source of the problem, fully depress the clutch pedal. If the jerking goes away, the vibration is caused by the clutch or transmission.
Note! Similar problems can arise when a “mechanics” or “automatic”, as well as a variator or “robot” breaks down.
Incorrect operation of some on-board computer sensors responsible for controlling the power unit can also cause shaking in idle mode. Check the operation of the sensors:
- mass air flow;
- crankshaft position;
- Hall;
- idle speed.
Another option is familiar to owners of cars with small engines. If powerful consumers (climate control system, heated seats) are turned on in such vehicles while idling, the engine may experience increased vibrations. They disappear as soon as the driver presses the gas pedal. The same effect can occur if the generator is damaged.
How do engine oil additives help with engine vibration?
Motor oil directly affects the quality of operation of the cylinder-piston group and the entire combustion process of the air-fuel mixture in the cylinder. Lubricity, detergent properties, uniform distribution over the surface and stability of the oil film are all key factors for the normal trouble-free operation of all engine parts. Additives that improve these properties of motor oil prevent the formation of scuffs, scratches and other defects on the friction surfaces in the CPG, and therefore contribute to the uniform operation of the entire engine without jerking and vibration.
Vibrations during braking
Pulsations and vibrations during braking can negatively affect vehicle handling and braking performance. And this is a serious problem, because the braking system is the most important system ensuring traffic safety. When contacting a mechanic regarding brake problems, be prepared to hear one of the following diagnoses.
Worn brake discs
Brake pads no longer adhere tightly to the surface of the discs if the latter are heavily worn (in which case they begin to wobble) or if they have different thicknesses. That is why, when the brakes are applied, the pads begin to slip, as a result of which the driver feels a pulsation in the brake pedal, and in most cases, also a beating of the steering wheel.
Solution: The brake discs must be repaired or replaced. To determine the direction of work, the disks must be inspected and measured. But in most cases, you have to replace a disc that has worn out so much that it has caused vibrations.
Worn brake drums
Brake drums that are out of round can cause the brake pedal to pulsate. Moreover, when you press the pedal, you may hear a squealing or grinding sound.
Solution: The drums need to be repaired or replaced. During the inspection, the mechanic inspects the drums for damage, such as cracks, scoring, or signs of exceeding thermal limits. The presence of any damage indicates the need to install new drums. In most cases, the drum will have to be replaced if it is worn enough to cause vibration.
Worn wheel bearings
Bearings allow the wheels to rotate while supporting the vehicle's weight. The brake disc is attached to the wheel hub with a bearing. If a worn wheel bearing has too much play, vibrations can be felt when braking. In addition, this has a bad effect on the car’s handling and the precision of its cornering.
Solution: Replace one or more worn bearings. The wheel bearing is usually an integral part of the wheel hub, so it cannot be replaced separately. In this case, you need to change the entire hub assembly.
Are all additives useful?
Not all fuel additives are useful and have a beneficial effect on the engine. Some not entirely honest manufacturers, even world-famous ones, follow the path of a little deception when, with the help of an additive, motor oil does not improve its physical and chemical properties, but only thickens. This is done to prevent oil from penetrating into the combustion chamber through chips and scratches, as well as to improve the distribution of lubricant over parts and stabilize the oil film, which, due to the reduced fluidity of the oil, remains on the rubbing surfaces longer.
Not a single professional service station technician will advise you on a thickening additive for motor oil. This is a temporary solution to the problem and, rather, even disguises it. Overly thick lubricant will even harm the engine in the long run. Each automaker recommends motor oil with certain mechanical and physico-chemical properties, since the operation of the engine of each specific brand is designed for certain conditions of lubrication, washing and cooling of its cylinder-piston group.
Changing such conditions will lead to overload and overheating of the engine, poor lubrication of the elements of its CPG and the washing off of carbon deposits from them. All this will certainly lead to serious damage and expensive repairs, although at first car owners notice positive changes.
Tips and tricks
As you can see, to prevent vibrations, regardless of whether the engine is carburetor or injection, it is necessary to maintain the cleanliness of the fuel system, the functionality of the ignition system, etc.
The fuel pump and ECM sensors, fuel and air filters deserve special attention; the fuel injectors, idle air valve, and accelerator pedal need to be adjusted. It is important to understand that vibrations that are not eliminated in a timely manner lead to the following negative consequences:
- cracks in the car body;
- gradual unscrewing of even the most tightly tightened nuts and bolts (which can lead to an emergency);
- premature wear of parts, resulting in, for example, oil leakage, destruction of bearings, seats, fasteners, etc.
We also note that sometimes motorists are faced with a problem such as a drop in speed to 500 rpm. on a warm engine at a rate of 750-900 rpm. As a result, the internal combustion engine begins to vibrate strongly. This indicates problems with the throttle and sensors (for example, TPS).
Also, drivers often deliberately lower idle speed to save fuel (especially if they have LPG). At the same time, the consequences of engine vibrations will subsequently lead to repairs, which in cost will cover all the savings on fuel.
Even while driving, it is important to consider at what speed to drive. The fact is that if the car is used incorrectly, vibrations can also occur. To prevent this from happening, you should adhere to the following rules:
- upshifting must be done between peak torque and peak power;
- when vibration occurs, it is necessary to switch to a lower gear to avoid engine damage;
- if the car does not pull, you must also switch to a lower gear, but do not allow vibrations to occur.
This approach will avoid premature wear of parts, while ignoring it will quickly damage engine pistons, transmission bearings, clutch basket, crankshaft liners, etc. Carbon deposits and wear appear on the walls of the cylinder liners; due to constant vibration, oil seals begin to leak, and shafts begin to run out.
Improperly secured motor
This is also one of the common reasons why vibration occurs in the body at idle. Most often, this problem is associated with wear and tear on one of the mountings on which the engine is mounted.
How to find out flaws in engine mounting? It's very easy to do. To do this, you need to open the hood and call an assistant to alternately engage neutral, reverse and forward gears. And at this time you should pay attention to the position of the engine on the supports. Thus, you alternately unload the pillows that hold the motor. With each new gear change, the engine will deflect in different directions at the same angles. If it deviates more than usual in any direction, it means that the pillow needs to be replaced in that place.
Let's sum it up
As you can see, the causes of engine vibrations at low speeds and idle pose a danger to the car engine and its individual parts. Any vibrations not only impair operating comfort, but also harm the engine.
Only timely recording of the above signs of vibration, immediate elimination of the causes, as well as regular technical inspection are the key to long and safe operation of the internal combustion engine and the entire vehicle.
Sources
- https://FB.ru/article/162048/vibratsiya-na-holostyih-prichinyi-i-metodyi-ustraneniya
- https://scart-avto.ru/remont/vibratsiya-dvigatelya-na-holostyh-oborotah-prichiny-pochemu/
- https://diagnozbibike.ru/neispravnosti-dvigatelya/vibracziya-dvigatelya-na-holostyh/
- https://nahybride.ru/dvigatel/vibratsiya-dvigatelya-na-holostyh-oborotah
- https://avtodvigateli.com/neispravnosti/vibraciya-na-xolostyx-oborotax.html
- https://dvigatels.ru/uhod/vibraciya-dvigatelya-na-holostyh.html
- https://avtodvigateli.com/neispravnosti/vibraciya-dvigatelya-na-xolostyx.html
- https://KrutiMotor.ru/vibratsiya-dvigatelya-na-malyh-oborotah-prichiny/
Diagnostics
Checking the power plant is done in this way.
Fastenings
Check that all bolts are in place and that they are tightened. Sagging cushions and loose axles in 60% of cases provoke the transfer of vibration to the body, imbalance of the internal combustion engine.
Fuel system
Checking the fuel lines is necessary to eliminate air leaks. Leaked bubbles are the primary source of interruptions in the normal engine stroke. For example, on a VAZ 2110 the “sore” is located in the fastenings of the fine fuel filter. It is also necessary to diagnose the carburetor or injector. A grain of sand stuck in an injector or jet prevents the normal flow of gasoline and disrupts the operation of the installation.
Bad fuel
Low-quality fuel is a common cause of car jerking and instability of engine speed. This usually appears a short time after refueling. The problem can only be solved by draining the fuel and flushing the entire system.
Engine
The next common problem is wear or incorrect adjustment of the main components of the power plant. Clogged strokes, a worn piston group or broken bearings can cause more than just jerking of the machine.
The problem of feeding the engine with the fuel-air mixture
Also a common reason for visiting a service station. Problems in the fuel and air supply system guarantee an unstable supply of the mixture to the combustion chamber. The result is a jerking of the car, floating speed of the power plant.
The problem can be resolved by diagnosing all elements of the fuel line, replacing filters, and checking the functionality of the fuel pump.
Engine management system
The following problem is relevant for vehicles equipped with an ECM. Sensitive electronics often malfunction due to wetness, mechanical damage, system errors, or incorrect sensor readings.
The fault can only be eliminated through computer diagnostics.
Electrics
The most common category of diseases is found in the electrical circuits of the machine. Here the master is required to consistently study the entire structure, from spark plugs to the ignition coil. On the injector you need to look at the ECM and then the ECU.
It is also important to measure the fuel rail pressure for the injector.
Ignition system
The most common cause in the system is wear of spark plugs and high-voltage wires. The ignition coils or electronics may also malfunction.
Diagnostics must be performed from the final element (plug) and along the line to the fuses.
Incorrectly set car ignition
The ignition timing affects the ignition point of the fuel mixture. If the adjustment is made late or too early, the engine loses power, jerks or stalls. A secondary symptom is the appearance of detonation.
Gearbox failure
If the gears in the device are ground, this can cause them to slip, and as a result, shocks when driving.
This is also often accompanied by extraneous sounds, vibration, and possibly knocking out of gears.
Damage to the accelerator (gas pedal)
Hall sensors and PCV sensors may work intermittently, which gives a false signal to the ECU.
If the problem is in electronics, you need to perform computer diagnostics, where all errors will be revealed.
In the event of a mechanical breakdown, all parts are thoroughly washed, dirt is removed and the equipment is repaired. Usually the problem occurs due to contamination of the damper drive.
Transmission breakdowns
Transmission units often cause the car to jerk during acceleration. When the car reaches a stable speed, the trouble is felt less or disappears altogether.
If the breakdown lies here, it is accompanied by the howling of the gearbox, increased noise and the appearance of vibration.
Clogged air and fuel filters
A trivial problem can be fixed literally for pennies. If the filters have not been changed for a long time, their throughput is significantly reduced. In this case, the engine may choke, stall, or slowly gain momentum.
Clogged or faulty injectors
Stable problem on injectors. The defect occurs due to the use of cheap fuel of dubious origin, or wear of the filters. Thin injector channels are prone to blockages, which prevents normal injection of the fuel mixture.
An additional factor is wear or breakdown of the electromechanical part of the injector. The device driver or wiring may fail.
Mass air flow sensor or crankshaft position sensor
Mass air flow sensor and DPKV are in second place in popularity when contacting service stations. The mass air flow sensor is located in the intake manifold and sends data to the ECU. The second sensor monitors the position of the crankshaft.
If these elements malfunction or fail altogether, the engine will not work correctly, constantly jerking or failing.
General recommendations for finding the cause of car jerking
The machine itself will tell you where to look for the problem. If the malfunction is accompanied by a hum or grinding noise, the defect is looked for in the mechanics. If there are no extraneous sounds, the problem is located near the motor.
An additional assistant here is the dashboard display. The appearance of lamps and indicators on the device can quite accurately indicate the source of the breakdown.
Fuel system contamination
If the spark plugs and wiring are in order, the engine is installed correctly, and the protective cushions are not worn out, but the engine still jerks at idle, the cause may be contamination of the fuel system. Of course, in order to affect the performance of the car, the pollution must be really serious.
The greatest danger is posed by excessive amounts of water, soot and oil. When parts of the fuel system become clogged, the HT mixture does not burn completely, as a result of which gasoline consumption increases significantly. In addition, the engine may “sneeze” and shake.
In this case, there is only one solution. This is a thorough cleaning and inspection of all elements and components of the fuel system.
