* Loose spark plug wires. If the spark plug wires are not properly tightened, they can cause the engine to misfire, which will cause the car to shake.
* Incorrect spark plugs. If the spark plugs you installed are not the correct type for your car, they can also cause the engine to misfire. Make sure to check your car's owner's manual to find the correct spark plug type.
* Damaged spark plugs. If the spark plugs are damaged, they will not be able to properly ignite the fuel in the engine's cylinders, which will also cause the car to shake.
* Vacuum leak. A vacuum leak can also cause the engine to run lean, which can lead to shaking. Check all the vacuum hoses in the engine compartment for leaks.
* Faulty coil pack. A faulty coil pack can cause the spark plugs to fire incorrectly, which can lead to shaking. If you have a faulty coil pack, you will likely need to replace it.
* Bad O2 Sensors. One potential cause of this could be a faulty oxygen sensor. Oxygen sensors play a vital role in the fuel injection process by monitoring the exhaust gas and providing feedback to the engine computer, which adjusts fuel delivery accordingly. If the O2 sensor is malfunctioning, it can lead to an incorrect air-fuel mixture and cause the engine to shake.
If you've ruled out all of the above possibilities and your car is still shaking after changing the spark plugs, it's best to take it to a mechanic for further diagnosis.
