What To Do If Car Shakes When Idle Or Driving At Slow Speeds?

How your car feels when you start the engine and begin driving is important. This is the time when you are most likely to notice unusual sounds or vibrations. All car engines vibrate to some degree, but it should be smooth. If your car’s idle RPMs are erratic or the car shakes when you are driving it needs some attention. If you ignore unusual car vibrations, it can lead to worse problems down the line.

A car engine needs the right mixture of spark, fuel and compression to give you a smooth ride. Many systems work together to create this precise blend of elements. If one of these systems fails your car will vibrate or shake, so this is a good place to start troubleshooting.

The most common reasons for a car to shake when idling or stopped are as follows:

  • Bad spark plugs
  • Worn spark plug wires
  • Loose or cracked timing belt
  • Loose or worn vacuum hoses
  • Fuel intake system / fuel filter problems
  • Loose or broken engine mount
  • Clogged air filter
  • Faulty mass airflow sensor
  • Bad radiator fan
  • Failing idle control valve

If your car does not start shaking until you begin driving, your problem may be in the tires or brakes:

  • Warped brake rotors
  • Worn brake pads
  • Imbalanced Tires

Sometimes your car may vibrate when at idle and stop when you reach higher speeds. Some issues that can cause this are:

  • Cold temperatures
  • Transmission problems
  • Dirty throttle body

The number of parts that can cause your car to shake may seem overwhelming. If your check engine light is on, ask your local auto parts store to read the code. This will help narrow down which area of the car may be causing your trouble.

Common Reasons with Solution for Shaking / Vibrating Cars

Fouled Spark Plugs

A bad spark plug is one of the most common causes of engine vibration and jerky acceleration. Spark plugs ignite the fuel in the engine, so when they fail fuel cannot burn at a consistent rate.

Check your spark plugs for oil, fuel or carbon deposits. Replacing any fouled spark plugs will usually fix the problem. You can find your spark plugs on the engine compartment connected to a bundle of cables.

Bad Spark Plug Wires

Spark plug wires send electrical current to your spark plugs. If these wires wear out, they can cause the same issues as bad spark plugs. Check your spark plug wires for cracking and replace as necessary.

Fuel Intake System Issues

The fuel intake system sends fuel to the engine after it passes through a filter. Over time the filter may become clogged with dirt and debris. This can cause an erratic flow of fuel to the engine, causing your car to vibrate.

Installation may be easy depending on the location of the filter. On older model cars you can try to find the fuel filter by following the fuel line. Some newer cars have a fuel filter inside the gas tank. In these cases, you may need assistance from a professional.

Loose or Damaged Vacuum Hose

Vacuum hoses relieve pressure from the engine by emitting exhaust fumes. When a vacuum hose is loose, broken or leaking your car may vibrate or shake.

You can find many vacuum hose problems by looking at the hoses themselves. If the hose is in good shape but loose, you may only have to tighten the clamp. If you see a hose that has become worn or broken, you will need to replace it.

Failing Timing Belt

The timing belt controls the flow and timing of air into your engine. If it has become loose or worn, it may cause your car to shake when idling or driving. You may also hear unusual sounds coming from the engine.

The timing belt is a flexible rubber chain with teeth on the inside to grip gears. Check the belt for signs of cracking or tears. You should also check the teeth inside the belt and ensure none are missing or damaged.

Replace the timing belt if it shows any signs that it is loose or worn. If the timing belt breaks, it can cause severe damage to your engine.

Mass Airflow Sensor

A faulty mass airflow sensor is one of the less likely causes of engine shaking. This sensor sends signals to the on-board computer with the correct ratio of air and fuel. If the sensor fails, your engine will receive the wrong amount of fuel.

The easiest way to check for issues with the mass airflow sensor is to put your car into neutral. If your car stops shaking in neutral, your problem is most likely the mass airflow sensor.

You can start by trying to clean the sensor. First pry the sensor out with a flat head screwdriver. Next, spray the sensor with isopropyl alcohol or specialized cleaner. Make sure that the sensor is completely dry before you reinstall it. If this does not resolve the problem, you will need to replace the sensor.

My Car Shakes When I Start It, Why? What Should I Do?

These are som common reasons why a car may shake when you start it.

Clogged Air Filter

The purpose of your air filter is to keep the air flowing into your engine free of dirt and debris. This helps keep your engine and fuel clean. Once the air filters become clogged the ratio of fuel to air will be incorrect. Check the filter for debris and replace if necessary.

Bad Radiator Fan

If your car shakes when the radiator fan engages this may be the cause of your car shaking. You may also experience an overheated engine or poor air conditioning performance. Both signs point to a broken radiator fan. If your engine overheats it can cause serious damage, so it is best to have your car serviced immediately.

Bad Idle Control Valve

The idle control valve manages your engine idle speed. This is how many RPMs your car runs at when it is idle. If your car shakes when idling, you may have a problem with the Idle Control Valve.

You may be able to clean the idle control valve to solve this issue. Use carbon cleaner or intake solvent. If this does not fix the problem, you may need to replace the idle control valve.

My Car Starts to Shake at Low RPM, Why? What Should I Do?

If your car is shaking when your engine speed is low, it may involve the brakes or tires.

Warped Brake Rotors

Brake rotors are round discs attached to your wheels. When you brake, this is what your brake pads close on to stop your car. If the rotors become warped the brake pads may have a difficult time gripping the rotors. This may also cause your breaks to overheat.

If this is your problem, your car will vibrate when you brake. If the damage is not too bad, a mechanic may be able to turn your rotors with a special machine lathe. If they are too warped or not thick enough you will have to replace the rotors with new ones.

Worn Brake Pads

Brake pads are the actual rubber pads that help stop your car when you press the brake pedal. If your brake pads have worn through or have uneven tread you may experience symptoms when you brake.

The car may shake and shudder, and you may even hear a grinding sound if you have worn them down to the metal. You could also feel the shaking in your steering wheel. A well-maintained braking system is essential for safety. Replace the brake pads as soon as possible.

Imbalanced Tires

When driving at high speeds, even a slight imperfection in your tires can make a big difference. Whether your tires are older or new, you should have them balanced on a regular basis. One sign that your tires are out of balance is a shaking when driving at high speeds. You may also have difficulty steering. Getting your tires balanced should fix these issues.

My Car Shakes When at Idle Then Smooths Out After Accelerating, Why? What Should I Do?

Cold Temperatures

Car engines do not operate well in the cold. When you start your car in cold weather it injects extra fuel until the engine warms up. Your car will idle at a higher rate until it reaches an appropriate temperature.

If your car stops shaking once you are farther into your drive, you may have nothing to worry about. If the shaking is severe long after the engine is hot, have your car serviced by a professional.

Transmission Problems

Both automatic and manual transmissions can cause your car to vibrate. If your transmission fluid is low, your car may shake during acceleration. Verify that you do not have a transmission leak and top off your transmission fluid.

Other transmission problems that can cause shaking are more serious. Your car may shake if you have trouble shifting gears. Your automatic transmission could also be shifting gears for no clear reason. In either case, you should have your car serviced by a professional.

Dirty Throttle Body

The air filter protects the throttle body to a certain extent, but it can still get dirty. When the engine shuts down exhaust fumes rise to the top of the engine. As the engine cools down, this can leave residue inside the throttle body.

In most cases you can clean the inside of the throttle body instead of replacing it. Follow the plastic duct up from the air filter to locate the throttle body. You can rotate the body housing to access the inside. Spray the inside with throttle body cleaner. After allowing it to sit for a few minutes, wipe out the deposits with paper towels.

It is never fun when cars don’t run as we expect them to, but this does not always have to mean costly repairs. As this article has shown, an overwhelming number of systems in a modern car can cause issues. I hope you have found that you can identify and fix many issues right at home. If your car is no longer shaking, we would love you to share your experience!

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