Engine vibration associated with fluctuating RPM is an annoying problem that causes engine torque to decrease and become unstable at idle, while driving in the city, or when stopped at a traffic light.
You’ll notice that when you stop and then want to accelerate, you’ll be surprised by a lack of engine torque and a strange vibration, which will force you to press the gas pedal hard to avoid stalling the engine.
There are several reasons why RPM can be unstable and unstable, including:
Faulty idle speed regulator (Idle speed actuator)
When RPM fluctuations occur, the first thing a driver should do is check the condition of the air control valve, as it is responsible for the air flow into the engine. most vibrations are caused by this valve.
In most modern cars, the air control valve and the inlet manifold door are all in one unit. Control is electrical, not cable-controlled, and everything is done through the car’s computer.
However, the part must be checked and cleaned, as dirt can cause it to malfunction.
Throttle position sensor failure
The throttle sensor is responsible for the throttle valve position. It sends the opening position to the car’s computer, which then sends the command to the injectors based on the position. This position is determined by the driver pressing the gas pedal.
Some damage to the throttle sensor may cause it to misread the position, confusing the car’s computer. This misreading can cause the injectors to vibrate and cause the engine to shake.
However, this is rare because the throttle sensor is a long-lasting component and rarely fails. However, to ensure the sensor’s integrity, it must be disassembled, inspected with a multimeter, and cleaned.
Clogged Air Filter
Dust accumulated on the filter can clog the passages through which air passes into the engine. This reduces the amount of air entering the engine, causing delayed combustion or incomplete fuel combustion, which negatively impacts the engine’s torque output.
You can notice when you press the gas pedal hard, black smoke coming out of the exhaust. This smoke is partially burned fuel. This causes the engine to consume a large amount of fuel, but in reality, it is a waste of fuel because the engine is not burning it.
Clogged Fuel Filter
Dust accumulated inside the fuel filter reduces the amount of gasoline injected into the combustion chambers. This causes difficulty starting and engine vibration. This vibration is accompanied by a decrease in engine torque, and you will notice the engine stifling and making a muffled sound.
Fuel Injector Failure
Partial or complete failure of an injector is a common problem with gasoline injectors. This is due to the small size of the fuel injection holes in the injector, as well as dirt and impurities that come with gasoline, especially in dusty and desert areas.
Therefore, injectors should be cleaned periodically, once a year or after a specific distance not exceeding 60,000 km. Fuel cleaners placed in the vehicle’s tank can be used without the need to disassemble the injectors.
Gasoline injectors are easy to disassemble and install, unlike diesel injectors. This makes cleaning and maintenance possible and accessible to everyone, even if you don’t have the necessary tools.
Fuel Pump Failure
A malfunctioning fuel pump can make it difficult to start the engine. However, if it stops completely, you won’t be able to start the engine without it. Initially, the pump’s performance decreases until it stops completely.
You will notice strong engine vibration. The reduced amount of fuel flowing to the injectors may cause the engine to run on only three cylinders. Typically, engine torque is weak, and the vehicle may stall while driving.
Mass air flow meter sensor malfunction
The Mass Air Flow Meter (MAF) sensor’s role is clear from its name: it calculates the mass of air flowing into the engine. This sensor enables the car’s computer to calculate the appropriate amount of fuel to inject from the injectors for complete combustion.
A dirty or damaged MAF sensor results in incomplete combustion and a malfunction in the combustion cycle.
Faulty spark plugs
Spark plugs cause fluctuations in engine RPM. Damaged spark plugs can cause numerous problems, including engine vibration. This occurs when one or more of the spark plugs are not working properly.
If they are completely damaged, you may find it difficult to start the engine, especially in the morning.
Faulty coil
The spark plug and coil can cause engine fluctuations and instability. The spark plug and coil generate a large amount of energy that it continuously distributes to the spark plugs throughout the engine’s operation.
Daily and continuous use reduces the spark produced by the alternator and distributor, leading to weak engine torque and instability.
Crankshaft sensor failure
The crankshaft sensor is located on the transmission side, near the gear wheel that drives the starter. However, it’s not the same gear, but a second gear behind the starter gear, which differs in the number and size of teeth. The crankshaft sensor’s role is to synchronize the piston’s up and down stroke with the spark plugs, which ultimately leads to engine ignition.
Camshaft sensor failure
The camshaft sensor is located at the top of the engine, specifically in the engine head. It works with the rest of the combustion system sensors, providing the car’s computer with the camshaft position to synchronize the fuel injection and spark timing.
A faulty sensor causes the engine to run with difficulty, with abnormal vibration noted, and the engine may not start at all. This malfunction is accompanied by a light on the instrument panel and the operation of the cooling fans in some types of cars.
Timing belt misalignment
The timing belt is responsible for synchronizing the engine’s internal components, allowing fuel to be injected into the pistons and subsequently ignited by the spark plugs.
This synchronization will not occur on time if the timing belt is not properly adjusted, causing the engine to either not start at all or to run with difficulty.
A vibration is noted in the engine due to delayed combustion in one of the pistons.
Incorrect timing belt alignment doesn’t occur suddenly, but rather occurs after a belt replacement or replacement of one of the pulleys around which the timing belt rotates.
Therefore, if you experience any of the problems we mentioned, this is a clear indication that the belt is not in the correct position, and it must be adjusted.
Faulty head gasket
Faulty head gaskets cause difficulty starting the engine, weak torque, and decreased coolant levels. Smoke with a somewhat unpleasant odor, which is incompletely combusted fuel, is also present. You will notice significant vibration and instability in the engine.
The intensity of this vibration varies depending on the degree of damage to the head gasket.
If the damage is to the cylinder, you will experience difficulty starting the engine, decreased coolant flow, noticeable vibration, and decreased torque, as the cylinder, which is leaking coolant, will not burn the fuel.
If the damage is to one of the oil holes, you will find that the coolant decreases as it mixes with the engine oil.
Damage to one of the engine head valves
The number of valves in the engine head varies depending on the engine type and manufacturer. The number can range from eight (8) to sixteen (16) valves in standard cars, but the number can be higher.
The valves are divided into two sections: the intake section, which houses the intake manifold and injects fuel into the combustion chamber.
The second section consists of the exhaust valves, which house the exhaust manifold and expel the combusted gases and smoke.
The valves operate by a reciprocating movement of opening and closing. Any defect in this movement results in incomplete combustion in the piston, which manifests as engine vibration.
The main cause of valve damage is the buildup of carbon on the valve resulting from fuel combustion, which causes it to become damaged and break. The other cause is poor quality valve materials or the expiration of its service life.
A problem with the rocker arms
The rocker arm, also known as the fingers in some countries, is responsible for determining the opening and closing times of the valve.
The rocker arms work in harmony with the camshaft, valves, and their compressors, all located in the engine head.
The rocker arms’ function is to apply pressure to the valve springs (the valve spring may be a spring or a metal cylinder with a return spring inside), which in turn applies pressure to the valves to open and close them.
This allows fuel to enter the combustion chambers and exhaust gases and smoke to escape, thus starting the engine.
The rocker arms are adjusted by a screw, and this adjustment is within a certain tolerance range determined by the engine manufacturer. Any misalignment in the adjustment causes the valve to open more or less than normal, or it may not close tightly.
This affects engine performance, as fuel consumption will increase if the valves are wide open, and vibration will be observed in the engine, especially during cold start-up.
An internal engine problem
One of the cylinders, camshaft, or crankshaft may be damaged. You can determine if the cause is internal by listening to the engine sound for popping, rattling, or any other strange noise accompanied by heavy smoke. Most faults caused by broken internal parts are accompanied by heavy, unusual smoke, a lack of coolant or engine oil.
Turning on the air conditioner
Turning on the air conditioner causes fluctuations in engine RPM. However, this isn’t a problem at all. Rather, it’s a deliberate action by the manufacturer.
The car’s computer increases the engine RPM according to the driver’s desired cooling level, ensuring the engine’s torque matches the new load, which is the air conditioner.
You’ll notice fluctuations in engine RPM when idling, but while driving, you won’t notice the difference.
Installing a Gas kit for your car (LPG)
Due to the high price of gasoline, many car owners, especially those with gasoline-powered vehicles, are forced to install gas.
This significantly reduces operating costs, with no noticeable difference between gasoline and gas in terms of torque. Some people believe that installing gas in a car causes the engine head to wear out quickly and shortens its lifespan. However, this is incorrect.
The evidence is that global companies like Volkswagen manufacture cars that run on both gas and gasoline without the need to install the kit at a workshop, as it comes pre-installed with the car.
Furthermore, gas has no negative impact on the environment and does not release significant carbon dioxide emissions.
We will not discuss the safety of the gas kit, its operating costs, and other issues, as these are matters of concern to the car owner, who is free to decide whether to install it.
What concerns us is the kit’s effect on the engine. In some cases, it causes engine vibration and fluctuations in RPM. This is due to an error in programming the flow of gas to the engine and its synchronization with the ignition spark.
This can lead the driver to assume the problem is with one of the spark plugs, the coil, or another component.
The reason for the programming error may be due to the technician who installed the gas kit, or it may be due to moisture resulting from rain or washing the engine, or due to the poor manufacture of the gas kit.
Whatever the reason, the solution is to have the gas kit checked by a specialized workshop and ensure that the gas kit’s computer is free of any problems at the programming or parts level.
If it is intact, then the problem lies elsewhere in the engine and not in the gas kit.
