Why is my Mercedes engine shaking?

In this blog, we will answer the question “ Why is my Mercedes engine shaking” and cover topics like what the research says, the issues causing abnormal vibrations in the engine, like worn out spark plugs, damaged engine mounts and other sub-topics mentioned further in the blog. 

Why is my Mercedes engine shaking?

Mercedes engines experience shaking or excessive vibrations due to being composed of many rotating mechanical and electrical components. When one of these parts malfunction, engines produce shaking (excessive vibrations), noticeable to the driver through the steering wheel or cabin especially during idling. 

During the ride, Mercedes engines face excessive vibrations due to a damaged or misaligned engine mount. These mounts can produce structural vibrations observable to the driver through the steering wheel. 

The major issues that cause shaking or abnormal vibrations in a Mercedes engine are outlined below:

  • Worn Out Spark plugs
  • Disconnected Hoses
  •  Damaged Engine mounts
  • Timing Belt Issues
  • Clogged Air Filter
  • Oxygen sensor malfunction
  • Clogged Fuel Injectors
  • Belt Tensioner Issues.

What does the research say about Mercedes engines vibrating?

Various scientific studies have determined that regularly occurring issues in an abnormally vibrating engine is the misfiring of spark plugs during idling and engine mount misalignment or damage that causes excessive vibrations in the cabin, generally noticeable to the driver through the steering wheel. There are several other issues (as mentioned above) that cause a Mercedes engine to shake or vibrate irrationally. 

Spark Plugs 

Spark plugs are used in gasoline engines to ignite the combustion mixture to create the explosion required for the engine to produce power. When one of the spark plugs in an engine is damaged, the fuel-air mixture is not appropriately ignited, thus leading to misfiring in the engine. Misfiring of the engine can cause abnormal vibrations. 

These vibrations can be witnessed during both ride and idling conditions. In idling conditions, the excessive vibrations will be more visible to the driver.

Bad Spark plugs causing sudden jerks and abnormal vibrations can also be recognized by the driver from the following:

Irregular idling of engine 

During idling, when the engine stumbles, it is known as rough idling

Misfiring of spark plugs

As discussed above, the firing order is interrupted which causes the vehicle to vibrate and halts the vehicle for a short span of time after which it accelerates.

Engine Surging 

The vehicle constantly starts and stops or decelerates automatically after giving sudden jerks.

 Vehicle starting trouble 

This can be seen in vehicles struggling to produce enough spark for ignition, causing the vehicle to produce crank noises without being able to kick off.

Just by replacing the spark plugs will stop the engine from experiencing abnormal vibrations. In a diesel Mercedes engine a glow plug is used instead of a spark plug. During failure, similar to a spark plug, the glow plug is replaced.

         Disconnected Hoses

Vacuum hoses help create a vacuum for air and fuel with a throttle that controls engine speed and airflow in the intake manifold. When one of the hoses are disconnected or worn out, engines can begin to misfire, cause rough idle, and an increase in RPMs. Simply by either reattaching or replacing, the problem can be solved.  

        Engine Mount

Engine or Motor mounts are one of the most integral components of a Mercedes engine as it attaches the engine with the chassis. If an engine mount is broken or misaligned from its original position, the vehicle will produce noises and vibrate very aggressively. This vibration corresponds to a structural vibration and the same is witnessed by the driver through the steering wheel

This can be observed by the driver if the engine vibrates excessively while the vehicle is in parking. Also, the driver can put the car in neutral and check if the vibration slows down, this process is a good indicator to verify if there is an issue with the engine mounts or not.

Mercedes uses an oil infused rubber mount for all engines to be fitted with the chassis. If the rubber portion of the mounts are damaged, it loses its vibrational and anti-wear properties and if the oil leaks into the other areas of the engine. This can become a potential hazard to the engine if they are not replaced soon enough.

If any of the above mentioned problems are faced by any user, it is advised best to immediately visit the service centre or a professional mechanic to inspect the engine and rectify the problem.

Timing Belt Issues

Any timing belt issues can cause your engine to vibrate. Certain components such as fans are driven by timing belts. When these belts are loose or worn, this can lead to an engine vibration in your Mercedes. Getting your timing belts checked out and replaced if necessary, will help to eliminate these vibrations.

Other methods to predetermine a damaged timing belt.

Misfiring 

This issue is common with defective timing belts when the belt slips on the cam drive. It causes the engine cylinder to open or close a valve earlier than it should which directly correlates with affecting the firing rate of the engine.

Squealing noises 

Occurs during braking

  Exhaust issues

 Ticking noise 

Occurs during acceleration

Clogged Air Filters

An air filter collects all types of pollutants that can be harmful to an engine. The more the air filter gets used, the higher is the amount of dust particles stored in the air filter. 

This clogs the air filter and impacts the sufficient amount of air flow to the engine for combustion. This runs a rich mixture (fuel > air) which may result in a rough idle and an increase in fuel consumption.

Oxygen Sensor Malfunction

Oxygen sensors are placed in front and behind the catalytic converter for measuring the amount of oxygen in the exhaust. This information is fed to the ECU to calculate the ideal air-fuel ratio for the most optimum combustion process. The sensors typically fail due to the following reasons:

  •  Accumulation of carbon deposits on the sensor.
  • Constant exposure to hot environments.
  •  Sensors used over a longer period of time tend to degrade and result in failure.

If an oxygen sensor fails, the ECU receives inaccurate information regarding the oxygen mixture and may cause the engine to run either very lean or very rich resulting in rough idle conditions. 

If the o2 sensor fails, it is noticeable to the driver through the check engine light in the odometer. The solution will be to replace the oxygen sensors to regain the optimum air-fuel mixture for the engine.

Clogged Fuel Injectors

Fuel injectors are generally designed to be as efficient as possible. High pressure fuel injectors are most commonly used in Mercedes engines as they dispense the right amount of fuel into the combustion chamber at the right time.

Since fuel injectors are exposed to high fuel pressures and temperatures, pintles get clogged by leftover carbon from the combustion process. 

This obstructs the fuel injector from dispense the optimal amount of fuel into the engine’s cylinder or may also affect the spray pattern, leading to rough idling and poor performance.

 

Belt Tensioner Issues

When a Mercedes engine is idling, a failed roller bearing or a belt tensioner causes abnormal vibrations or engine shaking. 

The crankshaft pulley, driving all the belt driven accessories, is generally known as a harmonic balancer or a vibration damper. 

The pulley slips if the rubber damper ring inside the pulley wears out, this occurrence can cause any belt driven component ( like the alternator pulley) to fail, resulting in abnormal vibrations as they constantly deteriorate.

The roller bearing of the tensioner can also fail, causing the serpentine belt to shred. By checking the belt tensioner’s movements, it is simple to determine if any pulley in that particular area is failing or not. Given below are some steps to diagnose a belt tensioner issue.

  • While one person gets behind the wheel, the other will need to stand in front of the car (with the hood open) to watch the engine.
  • With the emergency brake on and the car in Neutral, the driver will need to start the engine, and then rev it to 2,000 rpms for a few seconds.
  • If the spring-held belt tensioner starts to bounce or vibrate, it’s very possible that either its bearing or the pulley bearing of another accessory (such as the alternator or water pump) is failing.

The bearing fails in a belt tensioner since constant lateral force is applied on the belt tensioner from its spring action. Hence, the bearing is the simplest part to replace. However, it is important to check all the components that are belt-driven to ensure the belt tensioner’s failure is not a collateral damage from another pulley.

Conclusion

In this blog, we addressed the question “ Why is my Mercedes engine shaking?” We determined that there are more than one issue that lead to the abnormal vibrations or engine shaking in a Mercedes. Majorly worn out spark plugs and damaged engine mounts are the most common problems that produce abnormal vibrations in the engine. In addition to that, the article outlines in detail about each issue and provides a brief about why a certain issue has arisen and how to analyse and rectify the problem. 

Frequently Asked Questions (FAQs): Why is my Mercedes engine shaking?

  1. What does it mean when your engine starts shaking?

When an engine starts shaking, it experiences unusual or aggressive vibrations causing discomfort to the user of the vehicle. These conditions may occur due to worn out spark plugs or misaligned engine mounts or any other serious issue within the engine. 

  1. Can I drive my car if my engine starts  shaking?

No, Since driving the car while the engine is shaking can lead to major issues.  if the engine shaking occurs during idling conditions, then the issue might be due to worn out spark plugs or clogged fuel injector/air filter. This can cause the engine to surge or stumble before start or stop. 

If the unusual vibrations are felt during riding conditions, then the issue might be with the engine mounts. These vibrations can be very uncomfortable for the driver and if the rubber portion of the mount is damaged, it can increase wear and tear at the mounting points because of constant metal to metal contact.

  1. How much engine vibration is normal?

While Idle, the engine finishes more than 10 revolutions per second. A vehicle that operates normally measures about 1000. Since engines operate at high speeds, the gauge displays the counts as multiples of 1000.

  1. Why does my Mercedes shake when it stops?

A Mercedes vehicle shakes when it stops because of brake rotors. Brake rotors operate cohesively with the brake pads when the brake is applied by the user. As rotors age, it becomes thinner and when brake pads are pressed on the rotor then the vehicle shakes and comes to a halt.

  1. Why is my Mercedes shaking during acceleration?

A Mercedes vehicle shakes or vibrates excessively due to broken or misaligned engine mounts. While accelerating if any portion of the mount is broken, the engine can tend to slide away from its initial position. This can be very hazardous to the vehicle as the broken mounts put pressure on the remaining working mounts.

  1. How can I fix my engine if it is shaking?

         If an engine is shaking, it can be fixed by the following steps:

  • Find the conditions at which the engine faces shaking or abnormal vibrations.
  • If it is a speed related vibration. Then, maintain a constant speed in ride and then put the car in neutral, if the vibrations reduce, we can confirm that it is a speed related vibration
  • Check the vehicle if any misfiring or sudden jerks occur while idling or if the steering wheel is heavy and in constant vibration during the ride.
  • Take the vehicle to the service station and get the engine inspected if any of the above mentioned problems are faced.

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