Is your car doing the jitterbug when it’s supposed to be chilling?
If your car shakes when idle, it could be due to issues with the fuel system, engine belts, motor mount, or the air intake system.
Ignore it for long and it can lead to engine performance and accelerated engine wear.
What can you do about it?
Read on to explore why your car shakes when idle, how to resolve it, and other safety concerns.
This Article Contains:
- 10 Troubling Reasons Your Car Shakes When Idle
- How to Fix a Car that Shakes When Idle?
- 3 FAQs about Cars Shaking When Idle
10 Troubling Reasons Your Car Shakes When Idle
Here are common reasons that can make your car shake when idle:
1. Worn Spark Plugs
Spark plugs can wear out over time due to electrode erosion or carbon buildup. A worn spark plug results in incomplete combustion, engine misfire, and RPM fluctuation — causing your car to shake.
Note: You might also have idle shaking and misfire if your ignition coil is faulty. A faulty ignition coil may struggle to power each spark plug.
2. Damaged Engine Mounts
The engine mount (motor mount) is a frame that holds the engine in place. If the engine mount is worn, it won’t absorb engine vibration properly, and the car will shake while running.
3. Fuel System Issues
Fuel system issues can cause rough idle — fluctuating RPMs accompanied by abnormal engine vibration. This could be due to:
- Dirty fuel injectors: If a fuel injector becomes obstructed, it can’t dispense the correct fuel quantity from the fuel pump. A clogged fuel injector causes incomplete combustion and rough idling.
- Fuel intake valves: Clogged intake valves reduce fuel pressure and prevent the right amounts of fuel from entering the cylinder, causing rough idling.
- Clogged fuel filter: When fuel filters get clogged, they stop fuel from entering the fuel injectors. This reduces fuel pressure and prevents the fuel injectors from delivering enough fuel from the fuel pump to the engine.
A clogged fuel injector, fuel filter, or intake valve may also cause an engine to misfire and trigger the check engine light.
4. Air Intake System Issue
Air intake system issues can disrupt the engine’s idle speed and trigger an engine misfire, which translates to car shakes.
These issues include:
- A clogged air filter can restrict airflow, hampering combustion and straining engine components.
- A stuck idle air control valve can throw off the fuel mixture ratio, causing a rough idling engine.
5. Vacuum Leak
If there’s a hole in a vacuum hose (a vacuum leak), too much air enters the engine and affects the fuel mixture. This leads to a rough idling engine and triggers the check engine light.
6. Bad Oxygen Sensor
The oxygen sensor measures how much oxygen exits the exhaust. If the sensor is faulty, it sends inaccurate readings to the Engine Control Unit (ECU), and the resulting air-fuel mixture causes shaking due to inconsistent idle speed.
7. Worn Throttle Body or Sensor
The throttle body is a valve that regulates the amount of air that enters the engine. The throttle body position sensor monitors the valve’s position — sending feedback to the ECU.
Either part failing can throw off the air-fuel mixture, causing car vibration.
8. Catalytic Converter Issues
The catalytic converter converts harmful exhaust emissions into less toxic gases. If it becomes clogged due to a buildup of contaminants, it’ll disrupt the flow of exhaust gases. This creates increased backpressure, which affects engine performance and, in extreme cases, causes exhaust system shaking and car vibration.
9. Damaged Engine Belts
Issues with the drive belt and timing belt can cause your car to shake. Here’s how:
- A worn or misaligned drive belt will spin unevenly, sometimes causing steering wheel vibrations.
- A bad timing belt will throw the timing off between the components, causing shaking.
10. Faulty Alternator
A bad alternator causes an irregular power supply that affects components like the ECU, which controls your car’s idle RPMs.
Now that you know what makes your car shake when idle, let’s get your vehicle running smoothly.
How to Fix a Car that Shakes When Idle?
Fixing a car that shakes when idle requires some technical know-how. That’s why it’s best to have an experienced mechanic diagnose and address the problem for you.
A professional will conduct a visual inspection and check the diagnostic codes. Depending on the issue, they’ll:
- Tighten any loose mounts or components (spark plugs, suspension, etc.) to ensure they dampen engine vibrations.
- Inspect the spark plugs for damage or carbon buildup and replace them if necessary.
- Check if each vacuum hose is connected properly, ensure there are no leaks, and replace damaged hoses.
- Check engine belts for signs of wear, looseness, or misalignment. A shaking steering wheel can indicate a bad drive belt.
- Inspect the filters, intake valves, and injectors for clogging. They’ll clean or replace components as necessary.
- Assess the driveshaft. Your mechanic will replace faulty components related to the tires, like bad CV joints. This prevents shaking by helping your tires maintain stable contact with the ground.
Still curious about your shaky vehicle?
Let’s put any uncertainties to rest.
3 FAQs about Cars Shaking When Idle
Here are some important clarifications concerning a car that shakes when idle:
1. Is it Safe to Drive if My Car Shakes When Idle?
You shouldn’t drive your vehicle if you notice abnormal shaking since it can lead to:
- Poor engine performance: Faulty engine components can lower fuel efficiency, reduce power, and diminish engine performance.
- Increased wear: Driving with faulty components places unnecessary stress on your vehicle, leading to more damage.
- Safety issues: The underlying vibration issue could reduce your car’s safety on the road, either through reduced engine performance or problems with braking and suspension.
Ideally, you should have your vehicle towed or get a mobile mechanic to fix the vibration issue at your door.
2. How Much Does it Cost to Fix a Rough Idle?
Fixing abnormal car vibrations incurs varying costs, depending on the specific auto repair or replacement.
Here are some estimates for replacements (including labor):
- Spark plug: $15 to $230 per plug
- Air filter: $40 to $130
- Drive belt: $110 to $135
- Fuel filter: $70 to $150
- Fuel intake valves: $100 to $200 per valve
- Throttle position sensor: $250 to $450
- Idle air control valve: $120 to $500
- Oxygen sensor: $200 to $500
- Throttle body: $70 to $1,000
- Alternator: $100 to $1,000
- Vacuum leaks: $150 to $1,000
- Timing belt: $400 to $1,000
- Engine mounts: $400 to $1,000
- Fuel injector: $500 to $2,500
- Catalytic converter: $300 to $2,700
3. How Do You Prevent Your Car From Shaking When Idle?
Here’s what you can do to prevent issues that cause idle car vibration:
- Replace timing belt tensioners between 96,000 and 160,000 kilometers.
- Drive with moderate load to avoid premature wear and damage. If you notice a difference in braking and handling, there’s likely too much load.
- Follow essential engine maintenance practices, like using good quality fuel and getting a regular oil change. A regular oil change prevents components like the PCV valve from clogging and causing rough idle.
- Check for software updates since outdated software can cause ECM issues, which can affect your car’s idle RPMs.
Shake off Car Troubles with AutoNation Mobile Service
There are several problematic components that cause a car to shake when idle. However, diagnosing the issue is complex, so it’s best to consult a mechanic before driving your vehicle.
Looking for a convenient fix?
AutoNation Mobile Service will take care of your shaking car in your driveway.
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