Car Shakes When Accelerating – Causes, Diagnosis and How to Fix
If your car shakes when accelerating, the issue is usually related to the ignition system, fuel delivery, engine mounts, CV joints or wheel balance. This premium guide explains the most common causes and gives you a step‑by‑step diagnostic process to identify the problem accurately.
Symptoms
- Vibration only under acceleration
- Shaking between 20–60 km/h
- Shaking under heavy load or uphill
- Jerking or hesitation when pressing the gas pedal
- Check Engine Light may be on
Main Causes
- Engine misfire (spark plugs, coils, injectors)
- Clogged fuel filter or weak fuel pump
- Bad CV axle or worn CV joint
- Unbalanced or damaged wheels
- Faulty engine or transmission mounts
- Dirty MAF sensor
- Vacuum leak causing lean mixture
Step‑by‑Step Diagnosis
1. Check for Misfires
Misfires are the most common cause of shaking under acceleration. Use an OBD2 scanner to check for misfire codes (P0300–P0306). If present, inspect:
- Spark plugs
- Ignition coils
- Fuel injectors
2. Inspect Fuel Delivery
A weak fuel pump or clogged filter can cause hesitation and shaking. Symptoms include:
- Loss of power under load
- Long crank times
- Lean mixture codes
3. Check CV Axles and Joints
If the vibration increases with speed and is strongest during acceleration, a worn CV joint or axle is likely. Look for:
- Clicking noise when turning
- Grease around the wheel well
- Visible boot damage
4. Inspect Engine and Transmission Mounts
Broken mounts allow the engine to move excessively under load, causing shaking. Symptoms include:
- Clunking when shifting from P to D
- Engine movement when revving
5. Check Wheel Balance and Tires
If shaking occurs only at certain speeds, wheel imbalance or a damaged tire may be the cause. This is easy to diagnose at a tire shop.
6. Scan for Fault Codes
Use an OBD2 scanner to read stored DTCs. Codes related to misfires, air‑fuel mixture or MAF sensor can directly cause shaking under acceleration.
Relevant Fault Codes
- P0300 – Random/Multiple Misfire
- P0301–P0306 – Cylinder Misfire
- P0171 – System Too Lean
- P0101 – MAF Sensor Range/Performance
- P2195 – O2 Sensor Lean
When Is a Diagnostic Scanner Useful for Shaking Under Acceleration?
A diagnostic scanner is useful when the shaking is caused by an engine-management problem such as a misfire, lean mixture, airflow issue or fuel-delivery fault.
Use a scanner with fault-code reading and live data such as misfire counters, fuel trims and MAF readings. However, a scanner will not diagnose mechanical causes such as a worn CV joint, damaged axle, wheel imbalance or failed engine mount, so those components still require physical inspection.
When to Seek Professional Help
- Severe shaking under acceleration
- Misfire codes that return after replacing plugs/coils
- CV joint clicking or visible axle damage
- Fuel pressure below specification
- Engine movement due to broken mounts
