1. Engine Mounts: Worn engine mounts are a very common cause of shaking, especially noticeable at idle and when the engine is under load (like in Drive). They isolate the engine from the chassis. If they're bad, the engine vibrates excessively and transmits it to the car's body.
* How to check: Visually inspect the engine mounts for cracks, tears, or excessive sagging. A mechanic can usually assess their condition by rocking the engine.
2. Transmission Issues: A problem with the automatic transmission can cause vibrations. This could be due to:
* Low transmission fluid: Check the fluid level and condition. Low or dirty fluid can cause harsh shifting and vibrations.
* Torque converter problems: A failing torque converter can cause significant vibrations, especially at low speeds.
* Internal transmission problems: This is more serious and requires professional diagnosis.
3. Ignition System: Problems in the ignition system, such as:
* Worn spark plugs or wires: These can cause misfires that lead to vibrations.
* Faulty ignition coil: A failing coil can cause misfires in one or more cylinders.
* Distributor cap and rotor (if applicable): These components can wear out and cause ignition problems.
4. Engine Problems:
* Vacuum leaks: Leaks in the intake system can disrupt the air-fuel mixture, causing rough running and shaking.
* Mass Airflow Sensor (MAF) Issues: A dirty or faulty MAF sensor provides inaccurate readings to the engine computer, leading to poor performance and vibrations.
* Throttle Position Sensor (TPS): A malfunctioning TPS can cause erratic idling and shaking.
* Oxygen Sensor (O2 Sensor): A faulty O2 sensor can affect the air-fuel mixture, leading to rough running.
* Internal engine problems: This is less likely if the shaking is primarily at idle, but could include issues like worn piston rings or a problem with a connecting rod.
Troubleshooting Steps:
1. Check Engine Light: Is the Check Engine Light on? If so, get the codes read using an OBD-II scanner (available at auto parts stores). These codes will provide clues about potential problems.
2. Inspect Engine Mounts: Visually inspect them as described above.
3. Check Transmission Fluid: Check the level and condition of the automatic transmission fluid. If it's low, dark, or smells burnt, it needs to be addressed.
4. Listen for Unusual Noises: Pay attention to any unusual sounds coming from the engine or transmission while it's idling and running.
5. Basic Maintenance: Start with the basics: Change the spark plugs and wires (if they haven't been recently changed).
6. Professional Diagnosis: If the problem persists after checking these items, it's highly recommended to take your car to a qualified mechanic for a proper diagnosis. They have the tools and expertise to pinpoint the exact cause of the shaking.
Important Note: Ignoring a shaking engine can lead to more serious damage. Address the issue promptly to avoid further problems and potential costly repairs.
