Hey, Why Is My Car Shaking When Idle?

If you are short on time and want to fast-track the process to professional help, click Yes

Four common causes for a vehicle shaking while idle and their related parts.
Your vehicle is designed to operate smoothly without shaking or vibrating. When you start to experience a new vibration or shake, this is an early indicator that something is going on with your vehicle. Most commonly, the shake is coming from something that is failing on the engine, expressing itself through the amounts to the body, and it appears to be shaking the vehicle and is most noticeable with the engine in gear and your foot on the brake.

Is Your Car Shaking When Idle?

The shaking while idle is commonly caused by loose or broken engine mounts. However, it can also be caused by misfires in the engine due to carbon deposits and clogged fuel injectors.

Experiencing your car shaking while idle can be pretty disturbing. It's a clear sign that something is wrong due to various issues. Not only can this shaking be annoying, but it can also lead to potentially dangerous traffic situations. In addition, your vehicle's performance and handling may be compromised.

That's why addressing any shaking issues as soon as possible is essential to prevent further damage and expensive repairs in the future. Consider taking your car for a vehicle health inspection. By taking quick action, you'll maintain your and others' safety.

Let's Get To The Bottom Of It!

  • Q: Have the vehicle's fuel economy suddenly worsened?

    In a gasoline car engine, small parts called "fuel injectors" spray fuel into the engine before it ignites. Over time, these parts can get dirty and clogged from lack of maintenance. If that happens, the injector won't be able to spray the fuel, only dribble it out, making it harder to ignite. This causes the fuel to not burn completely in the engine cylinder, leading to lower performance and fuel economy.

  • Q: Do you need to push the gas pedal to start your vehicle?

    The idle air control valve is like a small motor that controls how much air goes into the engine when you're not pressing the gas pedal. This is important because you need enough air to help the engine run when you start your car. But if the valve gets stuck or breaks, it can close and shut out the air. This makes it hard for the engine to start, and you may have to floor the gas pedal to get it going.

  • Q: Is the vehicle idling faster than usual?

    The engine needs to know how much air is going into it to work correctly. This helps it determine how much fuel it needs to run smoothly. But if uncalculated air sneaks inside, it can mess things up. For example, this can make the engine idle (run without you pressing the gas pedal) weirdly. So, if too much air comes in, the idle might be too high.

  • Q: Is the "check engine" light on the dashboard?

    Engines in modern cars can put fuel directly into the engine part where it needs to go. However, this causes oil and gunk to build up on engine parts, preventing an ideal airflow. This buildup is called "carbon buildup" and can make the engine misfire. This can turn on the "check engine" light in your car.

  • Q: Do you see thin oily spots on your vehicle's parking spot?

    In your car, there are things called "motor mounts" that keep the engine in place and stop it from vibrating too much. Modern motor mounts have fluid to make them work even better. However, they can wear out and get hot over time, causing fluid leaks. As a result, you might notice black spots on the ground where you park your car.

Find Professional Help

Please select your vehicle's brand and location so we can locate the best professional help for you
If you are a shop owner and sick of business directories that are based on the cost of repair, AutoTechIQ is for you. If your customers receive Digital Inspection results then AutoTechIQ is definitely for you. Check out the certification page or how to rank in your area.

Vehicle Health Inspection Proof

Explore the following typical inspection results that show a potential cause for the symptom and select the one you believe is similar to your vehicle's issue.

Sagging motor mounts

The proof image shows the rubber on the motor mount has sagged to the point that the metal engine mount hits the metal frame causing the vehicle to shake.

A customer brought their vehicle to the shop and reported the engine was running rough and might need a tune-up.

The technician took the car for a test drive and noticed a lot of vibration through the vehicle when putting it in gear and pressing the brakes. However, they found no other issues related to the customer's concern during the vehicle health inspection.

To further diagnose the problem, the technician had an assistant get into the vehicle and, while in gear, torque the engine while pressing the brakes. They checked if the engine was moving excessively, but it did not appear to be.

Then, they lifted the vehicle on a hoist and manually pushed the engine at different locations to see if the vibration would disappear. It was found that raising the front of the engine eliminated the vibration.

Upon closer inspection, the technician noticed that the front engine mount had sagged and there was metal-to-metal contact. This means that the rubber on the motor mount deteriorated, and the metal engine mount was directly in touch with the car's metal frame, causing the vehicle to shake. Therefore, the front engine mount must be replaced to solve the problem.

Does the issue look like this? if not accessible your shop will document it
Shut idle air control valve

The proof image shows the idle air control valve and the connector used to verify that the IAC is sticking.

A customer dropped off their vehicle because they were having trouble starting it. They said they had an old car that would flood, and they would press the throttle pedal to the ground to get it to start. So they tried the same thing with this car, which eventually started but still had trouble idling correctly.

During the test drive, the technician noticed they had to open the throttle plate a little to start the car. Additionally, the technician noted that the check engine light was on. However, the vehicle health inspection found nothing related to the customer's concern.

The technician conducted a vehicle code scan and found a P0505 code, which means an Idle Control system malfunction. To further diagnose the issue, additional diagnostics were authorized.

The technician used a vehicle-specific scanner and verified the P0505 code. The technician then used the bidirectional controls to try to control the IAC (Idle Air Control), but the engine idle did not change when commanding the IAC.

To confirm that the command was getting to the IAC electronically, the technician attached an IAC tester to the IAC connector. The light on the tester showed that the command was indeed getting to the IAC electronically. Based on these findings, the technician determined that the IAC had failed and would need to be replaced.

Does the issue look like this? if not accessible your shop will document it
Vacuum leak

The proof image shows one vacuum line that is collapsed and another that is broken.

A customer brought their vehicle in, complaining it was idling at high speed, and they had to keep braking to prevent the car from moving by itself.

During a test drive, the technician found that the car had a high idle and its check engine light was on. The technician then performed a vehicle health inspection but found nothing related to the customer's concern.

To investigate further, the technician performed a vehicle code scan and found two codes: P0171 and P0174. These codes indicated a system lean condition in Bank 1 and Bank 2 of the engine.

With further tests authorized, the technician continued investigating the problem and found that the idle fuel trims were at -25 on both banks, indicating a significant vacuum leak.

To pinpoint the source of the vacuum leak, the technician started the vehicle and listened for hissing noises. The technician eventually found that a vacuum line on the back of the intake was broken, and another was soft and collapsed. The technician recommended replacing both vacuum lines to solve the high idle issue.

Does the issue look like this? if not accessible your shop will document it
Leaking motor mount

The proof image shows the failed hydraulic motor mount, the reason behind the vehicle's shaking.

A customer brought their vehicle to the shop and reported seeing a dark black substance leaking underneath it. They checked their engine and power steering oil, but everything appeared okay.

During the test drive, the technician didn't find anything unusual. However, during the vehicle health inspection, the technician discovered that both side motor mounts were leaking hydraulic fluid when the car was lifted on the hoist. This fluid was a dark black substance.

The hydraulic fluid was leaking from the motor mounts, which meant that the motor mounts had failed and needed replacement. Motor mounts hold the engine in place and absorb shock while driving. If they fail, the car can shake excessively, causing a rough ride and damaging other parts.

Replacing the motor mounts is essential not only for the sake of the leaking hydraulic fluid but also for the safety and longevity of the vehicle. The technician recommended replacing the motor mounts to ensure the car's safety and prevent further damage to the engine or other parts.

Does the issue look like this? if not accessible your shop will document it
Carbon deposit

The proof image is a photo taken with the borescope, which shows the excessive carbon buildup on the engine's valves, causing the misfire and resulting in worn spark plugs.

A customer dropped off their vehicle and reported that the check engine light had been on and would sometimes flash briefly, causing the car to shake. During the technician's test drive, they also noticed that the check engine light was on and that the vehicle was slightly hesitant and not as responsive as it should be.

After inspecting the vehicle, the technician found nothing related to the customer's concern. However, they scanned and found a random cylinder misfire code (P0300). Additional diagnostics were authorized, and the technician used a specialized scanner to verify the code.

The technician then looked at live data and discovered that the vehicle was inconsistently experiencing random misfires on several cylinders. The technician then inspected the spark plugs and found they were in good condition and not worn.

However, upon inspecting the valves with a borescope, the technician discovered they were heavily carboned due to a lack of maintenance. To address the issue, the technician recommended a GDI fuel service and upper intake clean to try and break up the carbon buildup causing the random misfire.

Does the issue look like this? if not accessible your shop will document it
Clogged fuel injector

The proof image shows the bottom of the injector nozzle is covered in dirt and carbon, damaging the car's fuel intake system and causing poor fuel economy.

A customer brought their vehicle to the shop, worried about their fuel economy. They used to get 28 miles to the gallon, but now only 24. They tried using premium gas, but it didn't seem to help.

On a test drive, the technician noticed that the RPMs on the tachometer were going up and down. However, they saw nothing about the customer's concern during a vehicle health inspection.

The customer authorized additional diagnostics to investigate the issue. The technician used a scanner specific to the vehicle and found that the RPMs fluctuated, but no diagnostic codes popped up.

To find the cause, the technician checked other live data and found the fuel trims were at -7, suggesting some fuel may not be burning. Next, the technician checked for misfires but didn't notice any.

Next, the technician checked the spark plugs and found that they weren't worn but were blackish. This suggested there was unburned fuel due to possibly dirty injectors, causing a bad air fuel mixture.

Finally, The technician recommended replacing the dirty fuel injectors, which the customer authorized. After the service, the technician verified that the RPMs became steady and clogged injectors were the reason behind the fluctuating RPMs and poor fuel economy.

Does the issue look like this? if not accessible your shop will document it

Typical Fixes to Address the Cause(s)

The following chapters bases themselves on experiences from our auto repair shop; we'll describe related problems' causes and fixes.

"Engine Mount Replacement" fixes "Sagging motor mounts"

The AutoTechIQ ranking for Safety, Cost Avoidance, and Environmental Impact is

env level
env level
Cost Avoidancei
env level
env level
Environmental Impacti
env level
env level
Hey, Why Is My Car Shaking When Idle?
Sometimes a problem is more challenging to describe than it initially looked like. If you are not sure your problem is described by this article, please find below similar vehicle symptoms, which might describe better the issue you are experiencing.

Other things your auto repair shop might talk about:

Fuel intake system. Timing belt. Steering wheel. Engine mounts. Car shakes. Rough idle. Engine vibrations. Idle speed. Replace spark plugs. Vacuum switching valves. Worn out spark plugs. Active engine mounts. fuel pressure. spark plug wire.