Your car idles when it is turned on and not in motion. The vehicle can be in gear when idling, such as when you’re stopped in traffic or at a red light. Or the car may be in neutral when idling – you may have the clutch pressed in if you have a manual transmission vehicle.
Unless your car automatically turns itself off when stopped with built-in stop/start technology, you will feel your vehicle vibrating slightly when it idles. This is normal. The older the car, the more you may notice the idling vibration.
But the car shouldn’t be shaking when it idles. There also shouldn’t be a knocking noise when your car is idling. Let’s look at what causes a car to shake when idling.
Can I drive my car if it’s juddering?
If your car is juddering while driving or idling, it is usually a sign that something is not functioning as it should. While it may still be possible to drive for a short distance, it is not recommended to continue using the vehicle without first identifying the cause. Juddering can be a symptom of issues ranging from engine misfires to drivetrain imbalances or faulty spark plugs, all of which can worsen over time and lead to more costly repairs.
If the juddering is mild and no warning lights are visible, you may be safe to drive directly to a repair centre. However, if the shaking becomes more severe or is accompanied by strange noises, dashboard alerts, or poor handling, it is safer to stop and seek professional advice before continuing to drive. Addressing the issue as quickly as possible will help prevent further damage and ensure your vehicle is safe on the road.
Why is my car shuddering when I idle?
A car that shudders while idling is often experiencing irregular engine combustion or poor air-fuel balance. This can be caused by a range of issues including misfiring spark plugs, a clogged fuel injector, or faulty sensors that confuse the engine’s computer. Even components like a dirty air filter or worn throttle body can lead to uneven engine performance, especially when the car is stationary.
While light vibrations are normal during idling, noticeable shaking should not be ignored. Over time, these symptoms can point to more significant mechanical or electrical issues. Get your car booked in with our mechanics to properly determine the exact cause and allow for a targeted repair.
10 of the most common reasons why your car shakes while idling
If your car shakes or shudders while idling, look for any warning lights or indicators on the dash. Pay attention to any strange odours, and look for smoke coming from the exhaust pipe.
1. Dirty Fuel Injectors
Fuel injectors that are clogged or obstructed by dirt or carbon cannot dispense the right amount of fuel needed for combustion. This may result in rough idling.
2. Worn Spark Plugs, Spark Plug Wiring, Ignition Coil
The spark plugs provide the ignition needed to start the engine, so if one is faulty or worn, the engine may react and cause the shaking.
Similarly, an ignition coil that is worn down over time may cause misfires.
3. Clogged Air Filters
Over time, your car’s air filters become full of dust and dirt. This then prevents proper air flow needed for the fuel mixture for combustion and could also lead to rough idling.
4. Air in the Fuel Lines
If you have a loose or missing gas cap, air will get into the fuel lines and may cause the engine to shake while idling. Also, excess air may enter the fuel mixture if you have worn-out rubber hoses under the bonnet.
Too much air in the fuel mixture can cause the engine to misfire, idle roughly or turn over high RPMs.
5. Worn throttle body
The throttle body is a small housing that connects to your fuel line and engine. It controls the amount of air that enters the engine to regulate combustion. The engine’s idle speed will be affected if the throttle body or its sensors are faulty or damaged. This may result in unnecessary vibration or rough shaking.
6. Oxygen Sensor
Your vehicle’s computer calculates the ideal ratio of air and fuel for the most efficient combustion process. An oxygen sensor relays information about how much oxygen is in the exhaust. If there is a breakdown in this sensor, the vehicle’s computer will receive incorrect information and affect the engine’s performance. Our auto electricians can analyse & diagonse underlying electrical issues.
7. Loose or Broken Engine Mounts
The engine is held in place by an engine mount frame that is designed to absorb the vibrations of your engine running normally. If part of the engine mount frame is broken or missing, you’ll feel the engine’s vibrations more.
8. Loose Battery Cables
There may be unnecessary cranking when you start the engine due to an insufficient charge from the battery. This might be caused by a battery cable that has come loose from the terminal.
9. Damaged or Slipped Belt
The fan belt – also called the serpentine belt – is a long rubber belt that transfers power to the engine accessories – the alternator, pumps, steering lines, air conditioning compressor, fans, etc.
It is powered by the engine so if it is loose, damaged or misaligned, it can create a vibration felt through the steering wheel.
10. Catalytic converter problems
Your catalytic converter filters out dangerous chemicals and toxins that come out of your exhaust. If it’s not filtering the exhaust properly, it can cause residue buildup that causes the vehicle to rattle when idling. You might need to repair your exhaust.
Can hybrid or electric cars shake when idling?
As you can see from the list of reasons above highlighting why a vehicle might be shaking or shuddering when idling, many different parts could be causing the rough idling.
Many of these components are present in hybrid or electric vehicles, so you may also experience shaking when idling with a hybrid or EV.
Can low oil cause juddering?
Yes, low engine oil can contribute to juddering, especially if the oil level drops below the minimum required for proper lubrication. Engine oil plays a critical role in reducing friction between moving parts. When the oil is too low, metal components inside the engine can grind against each other, leading to vibration, rough idling, and in some cases, serious engine damage.
In addition to juddering, you may notice the engine running hotter than usual or hear knocking sounds from under the bonnet. These are warning signs that should not be ignored. If your oil warning light comes on or you suspect low oil levels, check your dipstick and top up the oil as needed. For persistent issues, have a technician inspect the engine to rule out any further damage or oil leaks.
What to do if your car shakes when idling and when to see a technician
There are a few things that you can do yourself to try to stop the car from shaking when idling.
First and foremost, look to see what indicator or warning lights are on the dash. This will be your first clue of whether or not you need to see a technician.
Next, check your fuel cap and battery cables to see if they need to be tightened.
If you’re confident checking under the bonnet, have a look to see if your spark plugs look worn, if the air filters look like they need replacing, if the engine mount shows any obvious damage, and if the fan belt looks like it’s properly in place.
It’s best to have a technician look over these parts for you. If you’re unsure of what’s causing the shaking, you may do more damage by tinkering with the engine and parts yourself.
If there is no foul smell and no smoke coming from the exhaust, you can probably safely drive your vehicle our auto technicians. If you’re unsure, just give us a call on 0800 227 762 or email [email protected].