A car will usually shake under acceleration if there is a problem with the fuel system (bad injectors, blocked fuel lines or fuel filter), if there are problems with the wheels (unbalanced or worn tires), if suspension parts are badly worn.
A problem with your car can often be more apparent when you push the engine a bit while accelerating. Under acceleration, vehicle components are often put under extreme stress, and this is when older or worn out parts can show their age or even fail.
It can also happen if the brake system is not operating properly (siezed calipers, worn rotors) or if there is a problem with the engine such as faulty sensors or a vacuum leak.
9 Reasons Why You car shakes when accelerating
1. Problem with the fuel system
When you push down hard on the accelerator, a surge of fuel is needed to power the engine. If there is a blockage or leak anywhere in the fuel system, then the engine will not be able to get the correct amount of fuel that it needs and this can lead to excessive engine shaking as it struggles to stay running.
Common problems with the fuel system include faulty fuel injectors, blocked fuel filters and faulty fuel pumps.
Fuel injectors can become blocked by dirt present in the fuel and carbon deposits from leftover residual fuel can build up on their tips. These problems will affect how efficiently the fuel injector works especially under acceleration when more fuel is needed by the engine.
A dirty fuel filter will restrict the amount of fuel getting into the engine. This can make it more difficult to start the engine and can also restrict acceleration. A common sign of a dirty fuel filter is lack of acceleration or power when need it.
2. Worn Tires
The tires on your car are your only point of contact with the road. If the tires are not in good condition then you can expect a bumpy ride, and this will be especially noticeable when you are accelerating.
As a tire wears, the thread will decrease across the surface of the tire. This does not always happen in a uniform way, and this can cause a rough ride as the tire hits the road surface. A misaligned wheel will cause a tire to wear unevenly and this can cause the steering wheel to shake when going at certain speeds.
Another reason why a tire can cause shaking is if it is under inflated. An under inflated tire will have more contact with the road surface than it was designed to. This will affect how it wears and will also affect the handling of the car.
3. Badly Worn rotors/brake pads
Another common cause of shaking when accelerating is worn or warped brake pads. Brake rotors are precision engineered parts that need to sit perfectly flat on the wheel hub and must have an extremely flat surface for the brake pads to squeeze against.
Over time, brake rotors will wear and small ridges and other imperfections will appear on the surface of the rotor. These will cause the brake pad to wear unevenly as it the pad is softer and will take the shape of the surface of the rotor. If the surface of the brake pad is not smooth, then the pad will vibrate as the rotor turns against it. This can cause a vibration behind the wheel that you can feel in the steering wheel, suspension or brake pedal.
4. Seized Brake Caliper
Just like the brake rotors and brake pads, the brake calipers can also become worn and can actually start to stick.
The brake calipers on your car are responsible for squeezing the brake pads against the rotor when you push down the brake pedal. Calipers are operated by the brake fluid pushing against a piston that intern pushes against the brake pad.
Sometimes the rubber seals around the pistons can become torn or just wear from being exposed to heat and high pressures. This can cause the piston to seize in the caliper. If the piston doesn’t move smoothly, then it can cause the brakes to stay on after you have take your foot off the brake pedal.
5. Unbalanced Wheel
When you get a new tire or wheel fitted to your vehicle, it’s necessary to get the wheel balanced. In order to balance the wheel, one or more small weights are fitted to the inner rim of the wheel.
The weight that is fitted to a wheel is actually a counterbalance that is canceling out an imperfection in the shape of the wheel. Even if a wheel and tire are both brand new, they will still need balancing.
If a wheel is not balanced properly, or a weight falls off then the wheel will vibrate as it turns because it weighs slightly more on one side. This vibration will increase as you accelerate and can often be felt as a shake in the steering wheel at higher speeds.
6. Worn Suspension Parts
Worn out suspension parts and rubber suspension bushings are a very common cause of a car that vibrates when accelerating.
Most suspension parts consist of a metal part and a rubber bushing that dampens vibrations at the point where the suspension part is bolted to the subframe or wheel assembly. As the rubber bushing ages, it begins to lose its shape and can shrink and harden. As a result, the suspension part will become slightly looser and may start to move around and vibrate as you drive.
7. Faulty Engine Sensors
All modern engines rely on sensors that keep track of all areas of the engine. These sensors then relay that information to the vehicles ECU, usually in real-time, so that the ECU can make adjustments to the fuel and air supply components to keep the engine running smoothly.
If a sensor is failing, is dirty or is broken, then it won’t be able to work properly, and will give a bad or out of range reading to the ECU. This can wreak havoc with how the engine runs, leading to a loss of power, especially during acceleration. A badly running engine can vibrate and stutter and even cut out.
The most problematic engine sensors that can cause an engine to run badly are the mass air flow sensor (MAF sensor) and the manifold absolute pressure sensor (MAP sensor)
9. Problem With the spark plugs
Bad spark plugs are also a very common reason why your car shakes when accelerating. Spark plugs can fail in a number of ways and for a number of reasons.
An example of a dirty, worn out spark plug
The most common reasons are a carbon build up on the tips of the spark plugs, corroded or burned spark plugs and oil on the spark plugs.
The Cost Of Repairing A Car That Shakes When Accelerating
It can cost anywhere from $10 (the cost of getting a tire balanced) to a few hundred dollars if the fix involves new suspension or brake parts.
Here are a few sample repair costs, assuming you are carrying out the work yourself. If you are paying a mechanic to perform the repair you can expect to pay more.
- Replacement Fuel Filter: $10-$30
- New Spark Plugs: $40-$80.
- Wheel/Tire Balancing: Approximately $10 to get a wheel professionally balanced. Sometimes the problem is caused by a buckled wheel or a damaged tire. A replacement wheel or tire can cost hundreds of dollars depending on your vehicle.
- Replacement brake parts: $100+ dollars. If there is a problem with the rotors or calipers then it’s a good idea to change the brake pads also.
- Fuel system problems: Modern vehicles have more complicated fuel systems and can be difficult to troubleshoot. They are also more expensive to fix if the problem is not just a dirty fuel filter. Replacement fuel injectors can cost from $200 to replace with fuel pumps costing $400-$500 on some vehicles.
I’ve noticed my car shakes when I accelerate, and I’m trying to figure out the best approach to diagnose the issue myself before taking it to a mechanic. Can you offer some guidance on how I can start troubleshooting this issue on my own?
My car has recently started shaking when I accelerate, and I’m trying to figure out if it’s something I can fix myself or if it requires professional help. Could excessive engine vibration under acceleration indicate a simple maintenance issue I could address, like replacing spark plugs or balancing tires, or is it more likely to be a sign of a serious problem that needs a mechanic’s attention?