If your car starts juddering when you’re driving it can be very alarming, especially if you are driving at speed or on a busy road.
Many of us are unaware of what causes our cars to make this sudden movement and don’t know what to do to solve the problem.
Whether your car stutters or judders when braking, accelerating or even when idle, AA motoring experts have compiled a list to give drivers advice on what to do if they come across this problem.
Most causes of car juddering can be solved if caught early, so make sure to take your vehicle to a professional mechanic as soon as possible.
What does it mean when my car judders?
It all depends on context – a car juddering when slowing down might have a completely different issue to a car that judders when idle, or when speeding up. The reasons could include anything from an engine misfire to worn brake pads. To start to get an idea of what’s causing the juddering, make sure to make a note of what you were doing with your car when it occurred.
What is car juddering?
If a car is juddering, it means that there’s an irregular vibrating motion that you can feel through either your seat, the steering wheel or throughout the entire vehicle. This juddering can be a sign of an underlying problem with your car – which you should get checked out by a mechanic as soon as possible.
What’s the difference between juddering and shaking?
While there’s some overlap in meaning with cars that ‘judder’ or ‘shake’, there are some subtle differences you should look out for.
A car that judders will tend to have more of a rhythmic pulsing sensation that comes through the steering wheel, the seat or even through the pedals. It’s typically caused by one or multiple of the following:
- Brake issues
- Clutch problems
- Torque converter issues
- Engine mounts
- Fuel system issues
On the other hand, a shaking car refers to a more continuous and intense vibrating sensation that is felt throughout the entire vehicle, and isn’t limited to happening during a certain speed or driving action. This is typically caused by these issues:
- Unbalanced tyres
- Issues with the wheel alignment
- Engine problems
- Problems with the driveshaft
Why is my car juddering when idle?
If your car only judders when idle, it could be due to one of the reasons below.
1. Clogged air filter
The air filter’s primary purpose is to make sure that only clean air enters the engine. If the air filter becomes clogged or faulty, then the engine might not have enough clean air to function normally. This can present in inefficient combustion and juddering while idle. The car might also ‘run rich’, potentially causing rough running. In general, any issue with your air filter can cause the engine to have to work harder to draw in air – luckily though, this is a fairly simple fix at a garage.
2. Engine leaks
Certain parts of your engine are meant to be sealed, such as the intake manifold or vacuum hoses. If there’s an unintended gap between any of these parts, then a vacuum leak can occur, which can result in misfires, rough idling and car juddering. Other types of engine leaks that can cause juddering while idle include oil, coolant, fuel and exhaust leaks. Additionally, engine air intake leaks can cause fast idle or rough running where excess air is entering one or more of the cylinders. Leaks on the crankcase breathing system – such as those caused by a loose dipstick seal, can also cause the engine to judder at idle.
3. Ignition system fault
Faulty ignition system components such as ignition coil(s) and worn spark plugs are likely to cause an engine misfire, resulting in vibration throughout the vehicle.
Why is my car juddering when braking?
Juddering when braking your car could be due to a few specific reasons – read more about these below.
1. Brake discs
With sufficient wear and tear, brake discs can cause juddering. The older your brake discs are, the more heat they will have generated over the months and years, leading to potential warping and unevenness. When a warped brake disc makes contact with a brake pad, this can cause the vibrations and juddering that you might notice when braking.
The same can happen when brake pads are corroded, or fitted improperly.
2. Brake pads
As above, general wear can cause brake pads to become uneven and misshapen, leading to juddering when you apply your brakes. Other issues specific to the brake pads include clogging and contamination (with brake fluid, grease and oil) and glazing – where the pads are subjected to excessive heart and form a hard, shiny surface that reduces the braking efficiency.
Why is my car juddering whilst driving?
Here are some reasons a car might judder while you’re driving.
1. Dirty fuel injectors
Dirty fuel injectors can cause your car to judder as the engine’s performance and fuel delivery are negatively impacted. A dirty or clogged fuel injector means the engine is likely getting less fuel than is optimal for combustion – and can lead to juddering when driving. Additionally, an imbalance in the fuel mixture (too much or too little fuel from the injectors) can lead to juddering, rough idling and engine hesitation.
2. Fuel pump
Fuel pumps need to supply a consistent and adequate amount of fuel to the engine, so when they become worn or weak it can lead to juddering, reduced engine performance or even loss of power – making your car feel sluggish and unresponsive. To ensure your fuel pump isn’t damaged, avoid consistently driving with low fuel and make sure your engine/fuel system is regularly maintained and cleaned. Debris and clogging in the fuel system can cause numerous issues for your car.
3. Too much moisture
Excess moisture can negatively impact many parts of your vehicle. If components like the fuel system, clutch and drive belt are exposed to too much moisture or high humidity, this can result in juddering.
4. Blockages
Whether its the fuel system, the air intake, the exhaust system or the hydraulic system, blockages can cause erratic performance and juddering when driving. Fuel systems in particular can become blocked due to contaminated or aging fuel, low quality fuel additives and corrosion. The best way to avoid this happening is to have your car regularly maintained, and avoid leaving it for a long time with lots of fuel sitting in the tank.
5. Broken spark plugs
Spark plugs are vital for the engine’s combustion process, so when they’re broken or faulty, it can lead to misfires when one or more cylinders fail to ignite properly. This is what causes rough idling or juddering when driving or at idle.
Why is my car juddering when I’m pulling away?
If your car only judders while pulling away, these are some of the issues that might be causing it.
1. Issues with your clutch
If your clutch isn’t working perfectly, then it won’t be able to engage and disengage smoothly, leading to juddering when pulling away in your car. A worn clutch disc can cause this problem through general wear and tear – other issues that can contribute to this include clutch disc glazing (caused by excessive heat from overuse of the clutch), warped flywheels or pressure plates, damaged release bearings and broken clutch springs, to name a few.
2. Pressure plate defect
A normally functioning pressure plate applies pressure to the clutch disc, and has firm contact with the flywheel – this allows it to send power from the engine to the transmission. When a pressure plate is worn or has some kind of defect, it can mean there’s inconsistent or uneven engagement of the clutch, leading to juddering.
3. Issues with transmission
Issues with the gearbox, (or transmission) can cause juddering. In automatics, contamination of the transmission fluid or worn friction plates may cause the vehicle to judder. In manual cars, worn bearings or damaged gears could have a similar effect.
How to fix a juddering car
Before you get a professional mechanic involved, there are a few things you can look out for if you’re trying to self-diagnose why your car is juddering:
- Check if any warning lights come on – when you start your car, check the dashboard warning lights. If any come on (e.g. check engine) and your car is juddering, this can give you a clue as to what’s wrong. A flashing amber engine light is an indication that a misfire has been detected. This misfire will cause the engine to judder on idle and when driving.
- Carry out a visual check – inspect the engine bay, suspension components and undercarriage for any obvious signs of wear, damage or leaks.
- Carry out a test drive and listen for unusual noises – take your car out and put it through some different scenarios. If it only judders during a certain manoeuvre (e.g. while braking) then that will narrow down the possible causes of the problem. Additionally, make note of any knocking, ticking or hissing noises as these can be indicative of certain issues.
We don’t recommend attempting to fix any of the issues that can cause your car to judder on your own, if you have no experience with vehicle repair.
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