What Causes a Car's Engine to Shake?

A shaking engine is never good news, but some issues that shake our motor are worse than others. What are they?
Written by Andrew Koole
Reviewed by Kathleen Flear
background
A car engine on display in a mechanic’s shop.
Your engine vibrates at a certain level any time it’s running. If you
pop your hood
and notice those vibrations, you don’t have anything to worry about. But if you notice your engine shaking while you’re behind the wheel, that’s a problem you shouldn’t ignore.
A number of engine issues can result in an over-shaky engine, from relatively easy fixes to the worst news for any car owner—engine failure. 
Knowing the causes of these shakes can help you identify them if they should come up and prepare you for the potential
cost of repairs
before you reach the garage. The following are the most common reasons for a shaking engine, from least to most serious.

Worn out motor and transmission mounts

Your motor and transmission sit on mounts made of rubber that absorb a lot of your engine’s movements. Over time, these mounts can wear out and break.
If your mounts are in bad shape, you’ll likely notice excessive shaking and a clunking sound when your engine is running. Worn-out mounts don’t signal the end of your car, but they should be replaced ASAP to prevent that excessive movement from causing more damage.
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A misfiring engine

Every engine needs four things to run: air, fuel, spark, and compression. And all four of these elements need to be perfectly balanced for your car to run smoothly. 
If your sparkplug is worn out, your air/fuel mixture is off, or you have leaks affecting your compression, your engine can misfire.
Repairsmith
says people often assume that the sparkplug is always to blame for misfires, but that’s just not true. Any issue disturbing the balance of these three elements can prevent your car from starting or cause a misfire. A misfire could cause your car to “run rough” and shake.

Internal engine failure

No car owner wants to hear the three words above, but if your engine is shaking excessively, it might be what’s happening. 
Many things can cause engine failure, from a spun connecting rod bearing to a lack of oil. Not having enough oil in your engine can actually cause the friction that breaks parts and causes an engine to fail. 
Once you hear and feel your engine shake, rattle, and roll, there isn’t much you can do except pull over and call a tow truck.

Does car insurance cover these types of repairs?

Regular, mandatory
car insurance
does not cover repairs. But mechanical breakdown insurance, which is optional, can cover these types of repairs, depending on the policy.
To decide whether or not to buy mechanical breakdown insurance, you need to weigh the value of your vehicle to the cost of the coverage. You also need to know if you have an extended warranty on your car and what it covers if you do.
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