There are many reasons why your car may vibrate when running; it can be anything from unbalanced wheels to worn-out ball joints. However, vibrations occurring when the car is idle can usually be traced back to engine vibrations. And why would the engine vibrate? There are several causes of engine vibrations such as:

Faulty Fuel Injector System

The rate of flow of fuel from the tank to the combustion cylinder should be smooth and controlled. Anything that interferes with this smooth flow may cause poor idling, which you may feel as vibrations in the car. For example, if the carburetor is dirty or maladjusted, then it may be siphoning excess fuel one minute and less fuel the next. This will cause the engine to alternate between run fast and slow, which may cause vibrations. 

Damaged Timing Belt

A faulty belt, such as the timing belt, can also lead to engine vibrations. These belts control or turn other engine components, and if they are stuttering or not running smoothly, then the operations of the components they control will not be smooth either. For example, frayed, ribbed or cracked belts may cause these problems.

Damaged Engine Mounts

All combustion engines exhibit some level of vibrations due to the expansion of combustion gases and the movement of the pistons. Engine mounts, also known as motor mounts, are used to hold the engine in place and shield the rest of the car from these vibrations. If these mounts are damaged, then they won't be effective in shielding the car from these vibrations, and you may feel them from the inside of the car.

Misfiring Engine

A misfiring engine can also cause the engine to shake. Therefore, anything that causes misfiring will also cause engine vibrations. Some of the most common problems that cause engine misfire include:

  • Loss of spark – for example, bad spark plug wires
  • Loss of compression – meaning most of the air/fuel mixture escapes before it can be ignited; for example, if the gasket head is blown
  • Extremely imbalanced air/fuel mixture (discussed under "faulty fuel injector" paragraph above)

As you can see, there are myriad reasons your car's engine may be vibrating. Some of them point to serious damages, which may get worse if not promptly rectified. It would not be wise to assume, for example, that the fault lies with the fuel injector. Therefore, if your engine is vibrating, get a professional diagnosis and repair from your professional mechanic like one from South Pro Automotive Ltd.