Why Does My Car Shake When I Turn It On

It’s quite disconcerting when you start your car and notice it shaking. This can be an indicator of various issues, some of which are more serious than others. To understand the possible reasons and determine what’s happening under the hood, it’s crucial to dive into the mechanics of a car and look closer at each component. In this article, we will discuss the common causes of car shakes during startup, and outline the important points to consider when diagnosing the underlying problem.

Important Outline

1. Engine Misfires
One of the most common reasons for a car shaking while idling, especially during a cold start, is an engine misfire. When there is uneven combustion or a lack of spark in one of the engine cylinders, the engine will not run smoothly, causing it to shake. Misfires can occur due to several reasons such as faulty spark plugs, bad ignition coil, clogged fuel injectors, or improper fuel-to-air ratio.

2. Dirty or Damaged Spark Plugs
Spark plugs are responsible for igniting the fuel-air mixture inside the combustion chamber. Over time, they can become dirty or damaged, which can result in a weak spark or no spark at all. This can lead to misfires, incomplete combustion, and ultimately, a shaking car during startup. Replacing the spark plugs at regular intervals can help maintain a smoothly running engine.

3. Faulty Ignition Coils
Ignition coils provide high-voltage electricity needed to produce a spark at the spark plug. A faulty ignition coil can cause a weak or intermittent spark, resulting in an engine misfire. If you notice your car shaking during startup, it’s essential to check your ignition coils for wear and tear.

4. Clogged Fuel Injectors
Fuel injectors play a crucial role in delivering the right amount of fuel to the engine. Clogged or dirty fuel injectors can disrupt the fuel flow, leading to poor combustion and engine misfires. Regular servicing of your fuel injectors can help prevent this issue.

5. Motor Mount Issues
Motor mounts support the engine and transmission, absorbing vibrations and ensuring a smooth ride. Over time, they can wear out or become damaged, causing excessive vibrations from the engine to be felt throughout the car. A damaged motor mount may be the reason your car shakes during startup.

6. Vacuum Leak
The vacuum system in your car helps to maintain proper air-fuel mixture and provides power assistance to various components such as the brake booster. A vacuum leak can cause a rough idle and shaking during startup, as it disrupts the air-fuel ratio entering the combustion chamber. Diagnosing and repairing vacuum leaks is essential for maintaining engine efficiency.

7. Worn or Damaged Belts
Belts in your car engine transfer power from the crankshaft to various components like the alternator and water pump. A worn or damaged belt may cause your car to shake when turned on, especially if it slips off the pulley or causes imbalance in the driven component. Regular inspection and replacement of belts help prevent this issue.

In conclusion, a car shaking when turned on can be due to various reasons. It’s essential to diagnose the problem accurately and carry out the necessary maintenance or repairs to ensure a smoothly running vehicle. If you are not confident in diagnosing the issue yourself, always consult a professional mechanic for help.

Step by Step Guide

Here is a step-by-step guide to help you diagnose and address the issue of car shaking upon startup:

1. Take note of the symptoms: Before jumping into any diagnosis, it’s essential to note the specific symptoms you experience, such as when the shaking occurs (during ignition, idling, or acceleration) and its intensity.

2. Check for engine misfires: Start with the most common cause of shaking, which is engine misfires. Inspect the spark plugs, ignition coils, and fuel injectors for any signs of wear or damage.

3. Inspect the motor mounts: Visually inspect the motor mounts for damage or excessive wear. If you suspect an issue with the motor mounts, consult a professional mechanic for verification and replacement.

4. Look for vacuum leaks: Check for signs of vacuum leaks in hoses, gaskets, and other vacuum system components. Use a vacuum gauge or a smoke machine to help identify the source of any leaks.

5. Examine the belts: Inspect the belts for wear, stretching, or damage. Replace any belts that show signs of deterioration.

6. Consult a professional: If you’re unsure about the source of the problem or unable to diagnose it yourself, it’s always best to consult a professional mechanic for accurate diagnosis and repair.

Step by Step Guide with Bullet Points

– Record the symptoms
– Inspect for engine misfires
– Check spark plugs
– Check ignition coils
– Check fuel injectors
– Examine motor mounts
– Search for vacuum leaks
– Evaluate belts
– Seek professional assistance

Pros and Cons

Pros of diagnosing and repairing shaking issues:

– Improved engine performance
– Better mileage
– Enhanced vehicle safety
– Increased engine lifespan
– Better driving experience

Cons of diagnosing and repairing shaking issues:

– Potential repair costs
– Time-consuming process
– Inaccurate diagnosis, if not done properly
– Temporary fixes may require further repairs


Q: Can I drive my car if it’s shaking when I turn it on?
A: It is recommended to address the issue as soon as possible, as it might be an indicator of a more severe underlying problem. Driving with a shaking car can lead to damage or even accidents.

Q: How often should I replace my spark plugs?
A: It depends on the type of spark plugs you have. Copper spark plugs generally last up to 30,000 miles, while iridium and platinum spark plugs can last up to 100,000 miles. Always refer to your car’s owner manual for specific recommendations.

Q: Is it costly to fix a shaking car?
A: The cost of fixing a shaking car can vary depending on the root cause. It can range from relatively low-cost repairs, like replacing spark plugs, to more expensive repairs such as motor mount replacement or fixing vacuum leaks.


A shaking car during startup can be attributed to various issues ranging from engine misfires to worn motor mounts or belts. Accurately diagnosing the problem and carrying out maintenance or repairs is essential to preserve the efficiency and safety of your vehicle. While some car owners might be able to address certain issues themselves, it is always recommended to consult a professional mechanic if unsure or unable to identify the root cause. Regular maintenance and inspections can go a long way in preventing car issues, ensuring a smooth ride and a more extended engine lifespan.

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