Car Repair and Maintenance

Car Vibrates When Idle and Ac is On [Causes and Solution]

Car Vibrates When Idle and Ac is On

When your car vibrates when idle and AC is on, there is an issue that has to be fixed. The majority of people believe that this only occurs when there is a problem with the AC compressor. Knowing the engine components and how they interact with the AC compressor will help you fully comprehend this.

The vehicle’s AC compressor is an essential component. In hot weather, it cools the air inside a vehicle, creating a comfortable atmosphere for the passengers.

With this knowledge, it will be simple to recognize when the AC systems malfunction and how to avoid them. This article will explain why your car vibrates when idle and AC is on.

Car Vibrates When Idle and Ac is On

Car vibrates when idle and AC is on [possible causes]

The major reasons why a car shakes when AC is on are worn-out or broken engine mounts, a damaged AC compressor, and a poor fuel injector.

1. Faulty AC compressor

A car vibrates when idle and AC is on mainly because of a broken or malfunctioning car AC compressor. A car’s cooling system also requires an AC compressor.

Before supplying the proper amount of refrigerant to the condenser, the AC compressor raises the temperature of the refrigerant passing through the compressor.

A car’s engine is its main source of power. As a result, when the air conditioner is turned on, the engine starts to drive the car air control motor, which begins to deplete the battery power of the AC compressor.

When the air conditioning compressor in your vehicle breaks down, it may put too much strain on the engine and ultimately cause your car to shake when the AC is on. You must carefully examine the components of the vehicle’s air conditioner to identify the defective AC compressor that causes your car to vibrate while the air conditioner is on.

How to Fix

If the air conditioner in your car has been overfilled, you should immediately drain the Freon from the system. To solve the car’s shaking problem, it is crucial to avoid overcharged AC and damaged AC compressors.

2. Heavy engine load

Another reason a car vibrates when idle and AC is on is because of heavy engine load. The AC unit is connected to the engine. Additionally, AC compression is the main component of the cooling system and it is linked to the engine.

While the pressure rises beyond 400 PSI, the AC compressor begins to overload the engine, which causes your vehicle to vibrate when the air conditioner is on. The other components of your car can suffer damage or malfunction if the engine is under constant pressure.

You may immediately feel the shaking in the steering wheel when the air conditioning compressor in your car is started. When you switch on the air conditioning, your car rattles due to the stress placed on the engine, which also causes various component problems.

Additionally, the engine won’t be able to produce cold air if there is too much engine pressure.

How to Fix

The air conditioning compressor in your car should have routine maintenance to prevent load-on-engine problems.

3. Faulty fuel injector

An important part of the car engine is the fuel injector. Gasoline injectors use electronically controlled valves that may open and shut several times per second to spray fuel into a car’s engine. If you have a faulty fuel injector, you will notice that your car vibrates when idle and AC is on.

After turning on the AC, the engine must be properly fueled. While a vehicle’s fuel injectors aren’t working properly, the engine is strained due to a shortage of gasoline, which ultimately causes the car to shake when the air conditioner is on.

When the AC is on, even a malfunctioning fuel injector might cause your vehicle to idle harshly.

How to Fix

Your technician should always check the fuel injector if you take your car in for maintenance. A damaged fuel injector has to be updated often to prevent future problems with your car’s engine.

4. Defective spark plugs

Your engine’s power is generated by the spark plug via an explosion and a fuel/air combination.

When the AC is on, faulty spark plugs make a vehicle vibrate. Your vehicle vibrates more while it is idling and the air conditioner is on if the spark plug is broken.

In addition to wearing out over time, spark plugs also need to be changed between every 80,000 and 100,000 miles or once a year.

Check the owner’s manual for the replacement interval. Some automakers require a change at 18,000 miles, some at 30,000 to 35,000 miles, and others at 100,000, according to Kelley Blue Book.

Your car’s spark plug can be problematic if it can’t provide the engine ignition’s power or speed, particularly during the initial power generation.

How to Fix

The spark plug has to be changed in this situation.

5. Damaged or deteriorated engine mounting

The engine mount is a crucial part that keeps the gearbox and engine of your car in the proper positions. The engine and gearbox of a car are fastened together, and the engine mounts continue to hold them together and protect them from swaying.

As you may be aware, turning on a car’s air conditioning exerts a strain on the engine and the engine mount. The engine mounts might get worn down or shatter due to heavy strain. However, a damaged or worn-out engine mount cannot withstand the load strain, which is why your vehicle rattles when you put on the air conditioning.

Your car’s air conditioner can have other problems with a poor engine mount; the most typical one is a clicking noise. You must visit an auto repair shop and explain that your vehicle rattles while the AC is on and the engine is idle before they can replace the engine mounting.

How to Fix

The engine mounting often has to be changed if your car jerks while the air conditioner is on due to a damaged engine mounting.

6. Defective throttle position sensor

Another reason a car vibrates when idle and AC is on is the defective throttle sensor. The duty of a throttle position sensor (TPS) is to keep track of an engine’s air intake. The accelerator pedal’s location of the throttle position sensor determines how far open the throttle blade (or valve) can be.

The car’s defective throttle position sensor is unable to regulate the RPM (Revolutions per minute). Because of this, when you switch on the air conditioner in a vehicle with a malfunctioning throttle position sensor, your RPMs will fluctuate. If your car has this problem, it may vibrate when idling and have unstable RPMs while the AC is on.

How to Fix

Check the TPS:

The first thing to do is to check the TPS to see if it is the problem. You can check the TPS with a diagnostic tool or by taking your car to a mechanic.

Replace the TPS:

If the TPS is broken, it will have to be changed. You can get a new TPS at an auto parts store near you or online. It’s important to get the right TPS for the make and model of your car.

Install the new TPS:

Once you have the new TPS, you will need to put it in your car. Depending on the make and model of your car, this process may be different, so you should look at the manufacturer’s instructions or talk to a mechanic.

Test the car:

Once you’ve put in the new TPS, you should test the car to make sure the problem is fixed. Start the car and let it run with the air conditioning on to see if it shakes. If the shaking stopped after replacing the TPS, the problem was likely fixed.

7. Disconnected or Loose Hoses

Those of you who are unaware of what homes are in your vehicle. The hoses, constructed of flexible rubber, are the cooling system’s (the air conditioner’s) weakest structural component.

The hoses on your car may be disconnected from the engine mount or loose for various reasons. The car trembles when the AC is turned on when the hoses are removed from the support.

How to Fix

You should tighten and reconnect any detached or dangling hoses after inspecting them.

8. Dirty throttle body

The throttle body controls how the air flows through your car’s engine. The throttle body is located between the car’s air filter and the intake manifold. When you have a dirty throttle body, you will notice that your car vibrates when idle and AC is on.

Car engines can’t receive enough airflow, but the throttle body is an air-passing component that may become filthy rapidly.

How to Fix

Therefore, when you switch on the air conditioning, your car vibrates because the engine is unable to get appropriate airflow. Cleaning the unclean throttle body and addressing the shaking while the air conditioner is on.

  • Turn off the engine. Make sure the engine is off before attempting to repair a car that vibrates while the AC is on.
  • Look under the hood for the throttle body. You must now find the throttle body by opening the hood of your car once it has stopped. You will notice that your throttle body needs to be cleaned because of dirt.
  • Don’t start your car but leave the key in the “ON” position. Ensure you don’t turn the vehicle on; leave the ignition key in the “on” position. You won’t be able to clean the throttle body after starting the engine.


Why does my car misfire when the ac is on?

Since the engine’s air conditioning receives torque, the AC compressor is responsible for your car’s misfiring. The compressor clutch is triggered when the air conditioner is turned on. When you turn on the AC, the engine’s RPM decreases, and the car’s actuator opens to let more air into the engine. As a result, when you switch on the AC, your vehicle may misfire if the AC compressor isn’t operating correctly.

Why does my rpm change while the ac is on?

The engine is under much strain from several components, particularly when the air conditioner is turned on. For instance, the AC compressor puts a great deal of pressure or load on the car’s engine, which often causes the RPM to fluctuate when the AC is on.

Your car’s RPM fluctuates when the air conditioner is running for a variety of reasons, including a faulty AC compressor, a bad belt, or an overfilled AC system.

Why causes rough idle when ac is on?

When you switch on the air conditioning, your vehicle can sometimes idle poorly. This is a common issue for car owners. A filthy throttle body, a broken condenser fan, an old spark plug, worn-out engine mountings, or a broken IAC valve are to blame for your car’s poor idle while the AC is on.

When your car vibrates when idle and AC is on, examine these components to see which one is to blame. You can eliminate your car’s rough idle while the AC is on by thoroughly cleaning the majority of these parts of the vehicle.

Final words

So we have seen why a car vibrates when idle and AC is on, which is a typical problem with vehicles. Before replacing your car’s air conditioning because it is vibrating, you should investigate each possible reason. Your expertise also aids in detecting the cause of your car’s trembling while the AC is on.

The most frequent causes of why a car shakes while idle and the AC is on.  are an excessive load on the engine, a malfunctioning air conditioning compressor, and a damaged fuel injector.

Everyone is aware that dealing with a vehicle-related problem will cost you a lot of money and effort. That’s why it’s usually a good idea to figure out what is causing the car to tremble before doing anything else. When you figure out why your vehicle vibrates when idle and AC is on, you shouldn’t wait for it to go away on its own.

If you can’t solve the vehicle vibrating problem alone or have the necessary knowledge, take it to an auto shop. If your car shakes while the AC is on, immediately take it to a mechanic since waiting too long won’t solve the problem.


Latest posts by Bernard Juchli (see all)

Bernard Juchli

Bernard Juchli is an experienced racer, mechanic and team owner who trusts Avon Tyres.Bernard is the lead driver and force behind his Big Dog Garage Race Team. He is the General Manager and Chief Mechanic of Jay Leno’s Garage. Bernard and his crew of seven are responsible for all repairs, restoration and fabrication of Jay’s incredible automobile and motorcycle collection.

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