While Sitting Still (Engine Running):
* Engine Mounts: Worn or broken engine mounts are the MOST likely culprit for shaking while idling. The engine mounts isolate the engine from the chassis. If they're bad, the engine vibrates excessively and transmits that vibration to the car's body. Inspection: Visually inspect the engine mounts for cracks, tears, or excessive sagging. A mechanic can often perform a simple "rocking" test to assess their condition. Fix: Replace the engine mounts. This is a relatively common and usually not overly expensive repair.
* Engine Misfire: A misfire (one or more cylinders not firing properly) causes uneven engine operation and shaking. This can be due to:
* Spark plugs: Worn, fouled, or damaged spark plugs are a common cause. Inspection/Fix: Inspect and replace spark plugs as needed.
* Wires: Damaged or loose spark plug wires can prevent proper spark delivery. Inspection/Fix: Inspect for cracks or loose connections and replace as needed.
* Ignition Coil: A faulty ignition coil (or coil pack) can cause misfires. Inspection/Fix: Testing requires a multimeter or diagnostic scanner. Replacement is often necessary if faulty.
* Fuel Injectors: Clogged or malfunctioning fuel injectors can lead to misfires. Inspection/Fix: This is more complex and usually requires specialized tools and knowledge. A fuel injector cleaning or replacement might be needed.
* Sensors: Various engine sensors (e.g., crankshaft position sensor, mass airflow sensor) can contribute to misfires if faulty. Inspection/Fix: Diagnostic scanner is needed to check sensor readings.
* Balance Shaft: Some engines have balance shafts to reduce vibration. If this is failing, it'll cause significant shaking. Inspection/Fix: Requires specialized knowledge and tools to diagnose and repair.
While Driving (In addition to when sitting still):
The shaking while driving could be related to the engine issues above, but it could also involve:
* Tires/Wheels: Unbalanced tires or wheels are a common cause of vibration, especially at certain speeds. Inspection/Fix: Have your tires balanced and check for bent rims.
* Driveshaft: A worn or damaged driveshaft can cause vibration, particularly at higher speeds. Inspection/Fix: Requires a mechanic's inspection.
* Wheel bearings: Worn wheel bearings can produce a rumbling or shaking sensation. Inspection/Fix: A mechanic can diagnose this with a thorough inspection.
How to Proceed:
1. Start with the easy checks: Visually inspect the engine mounts. Check the tires for wear and balance.
2. Diagnose engine misfires: If the shaking is primarily when the engine is running, even when stationary, have a mechanic use a diagnostic scanner to check for misfire codes. This is the most cost-effective approach to rule out more serious problems.
3. Professional diagnosis: If the problem persists after checking the simple things, take your car to a trusted mechanic. They have the tools and expertise to properly diagnose the cause of the shaking and recommend the appropriate repairs.
Important Note: Ignoring a shaking car can lead to more serious and expensive problems down the line. Address this issue promptly.
