Why does my car engine shake when idling?

This blog post will answer the question, ‘Why does my car engine shake when idling?’, and cover topics like what does a car engine shakes when idle mean, what causes a car engine to shake when idle, different cases of a car engine shaking when idle, and how to fix a car engine shaking when idling.

Why does my car engine shake when idling?

These are the following reasons that are responsible for a car engine shaking when idling:

• Fuel injectors are dirty or clogged
• Defective spark plugs
• Vacuum leaks
• Clogged catalytic converter
• Air filters are dirty 
• The distributor cap has moisture on it
• Defective fuel pump
• Loose engine motor mountings
• Faults in the mass airflow sensor(MAF)
• Car accelerator cable is worn out or damaged
• Defects in the transmission control module
• Driving a car with a stick shift

What does a car engine shaking when idle mean?

A car engine shaking when idling can be described as a sharp shaking motion of the car for a brief period of time either while idling, accelerating the car, or shifting gears and is also known as rough idling.

A rough idling problem in a car should be taken care of with immediate effect, as it can indicate that the car is running out of gas or it has multiple damaged or worn-out parts. 

What causes a car engine to shake when idling?

These are the following reasons that contribute to a car engine shaking  either while idling, accelerating, or shifting to higher gears.

Fuel injectors become dirty

Fuel injectors in a car provide a continuous flow of fuel for optimum mixing with air inside the combustion chamber of the car engine. If they become clogged or dirty, the engine will be deprived of an optimum mixing ratio of air and fuel and thus produce lesser power causing the car to resist moving any further.

Defective spark plugs

Spark plugs in an engine help to ignite the air-fuel mixture in the optimum ratio and cause the pistons to move downwards, producing power that is transferred to the wheels via the crankshaft.

The spark plugs if defective or worn out can cause the engine to lose the igniting spark and thus result in the production of lesser power and cause the car engine to misfire and vibrate.

Clogged catalytic converter

The catalytic converter is a crucial part of a car as it filters the harmful and hot exhaust gases containing carbon monoxide and nitrous oxide gases into acceptable compounds like water and carbon dioxide.

Sometimes the catalytic converter can get clogged and hinder this process causing the car to jerk or vibrate, and can also potentially leak harmful gases like carbon monoxide into the cabin, which can be potentially fatal for the occupants within. 

Dirty air filters

Air filters are necessary for maintaining the correct mixture of the air-fuel mixture in the car to burn optimally. In case the air filters get dirty or clogged with debris and gunk buildup, it can interfere with the mixture ratio and make it shake.

Moisture on the distributor cap

The distributor cap is a crucial part of the car ignition system as it supplies electricity to the car to start it. If moisture happens to find a place on the distributor cap, it can stop working and send electricity, thus causing the car engine to shake.

Defective fuel pump

The fuel pump is responsible for regulating the flow of fuel into the engine for optimum combustion of the air-fuel mixture inside the combustion chamber. 

A clogged or damaged fuel pump will hinder this process and the combustion chamber will have inadequate fuel supply, leading to improper combustion and less power produced.

Faults in the mass airflow sensor(MAF)

The mass airflow sensor(MAF) is responsible for keeping checks on the amount of air entering the combustion chamber. It sends this information to the ECU, after which the fuel injectors send the optimum amount of fuel for mixing.

In the event of a car shaking or jerking at high speeds or during accelerating, it might be due to a faulty mass airflow sensor(MAF).

Car accelerator cable is worn out or damaged

In some cars, the car is accelerated with the help of an accelerator cable that acts as a link between the gas pedal and a throttle plate. 

When the gas pedal is pressed, the cable pushes the throttle plate, causing more fuel to be injected in the combustion chamber, thus causing the car to accelerate.

Driving a car with a stick shift

In the case of a car that is operated using a stick shifting system, a shaking motion in the car engine is often observed while changing from a lower to a higher gear.

Different cases of a car engine shaking when idling

The following are the different conditions of a car engine shaking when idling:

• When the car is accelerating
• When the car is shifting gears
• When the car is at lower revs
• When the car is in idling position

How to fix a car engine shaking when idling?

A car engine that is shaking when idling can be fixed in the following ways:

• Perform manual cleaning or replacement of the dirty fuel injectors
• For a clogged catalytic converter a replacement is ideal, however it is a costly investment
• Consider replacement of defective and worn out spark plugs
• Clean the air filters thoroughly in case of clogging
• Consider replacing the fuel pump if it is damaged
• Replace the worn out or slacking car accelerator cables as they are crucial for the car to enter higher speed ranges
• In case of moisture buildup on the distributor cap, instead of replacing it, allow it to sit for a while so that the moisture evaporates

Research has shown the ways to fix a car engine sputtering under various driving conditions. 

Conclusion

This blog post addressed the question, ‘Why does my car engine shake when idling?’

We understood what a car engine shaking during idling actually means and looks like. We also came across different causes behind this scenario. Furthermore, the different driving conditions of a car engine shaking when idle and the ways to fix a shaking car engine have also been discussed. Please feel free to comment on the content or ask any questions in the comments section below.

Frequently Asked Questions(FAQs): Why does my car engine shake when idling?

Why does my car shake while stopped?

The primary cause behind a car engine shaking when stopping are defective or worn out spark plugs, vacuum leaks, and even broken or loose engine motor mountings that hold the engine in place.

Why is my car shuddering when I accelerate?

One of the main reasons behind a car engine shuddering while accelerating can be loose engine and transmission mounts.

What does a loose spark plug sound like?

A loose or worn-out spar plug can often cause a characteristic fluttering sound.

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