Engine Vibration Causes – Free Auto Repair Tips
July 25, 2009 4:51 pm DIY, How To Auto Repair 
This Kia Rio had a severe engine vibration, see the picture below for the cause.
There are several things that can cause an engine to shake. If there is an engine vibration problem, typically it gets worse with the air conditioning turned on since there is more of a load on the engine. In this auto repair article, we will cover several things that can be looked at to help diagnose the problem. Misfires can definitely cause an engine to shake, usually in most late model cars a misfire will almost always be accompanied by a CEL (Check Engine Light) and misfire code. Many times if the engine also stalls, there could be excess carbon build up on the throttle plates or IAC (idle air control motor). Cleaning the throttle body and IAC is a common practice when trying to eliminate possible causes of engines vibrating.
Broken engine and transmission mounts can often be the cause of clanking, thumping and shaking. What the engine and transmission mounts actually do, in addition to securing those major components is to isolate the vibrating sensation and keep the passenger compartment as smooth and as vibration free as possible. It’s the same idea with exhaust hangers that have rubber incorporated into them to reduce and isolate vibration. This is the reason that some automobile manufacturers call them insulators and not motor mounts. One cause of failure can be that the rubber in the mount has collapsed, greatly reducing their ability to absorb vibration from the engine or transmission. Collapsed mounts are the hardest to diagnose, since the rubber may not appear to be worn. Typically when checking engine mounts, one person will be in the driver’s seat power braking while an assistant checks for excessive movement in the mounts. This can be dangerous if the person in the driver’s seat accidentally slips off the brake. Extreme caution is advised. Checking the mounts with a light that can provide plenty of illumination is recommended.
- While power braking in drive and reverse, broken mounts may show more movement in one direction or the other.
- Check for worn mounts while rocking the car back and forth with your legs pushing on the bumper. This is a quick check that is easy to do by yourself with the engine off and the car in park.
- If you choose to check the mounts by rocking the car, make sure that the hood is supported well. More than once, I’ve caught the car hood as it fell due to weak hood shocks.
- Some motor mounts can be diagnosed just with a visual inspection. Look for splits or tears in the rubber.
When changing motor and transmission mounts, the car needs to be well supported. If a vehicle lift is not being used, floor jacks need to support the car. Then use 2×4 block of wood on a floor jack place under the oil pan or transmission. Alternatively the engine can be suported by an engine support bar from the top-side. If a vehicle lift is being used, tall jack stands or jack screws under the car can be used to allow more comfortable working conditions.
Tools Needed to Check & Change Motor Mounts
- A good flashlight or drop light.
- Floor jack and/or jack stand.
- Vehicle lift is preferred but not always necessary.
- Jack screw or tall jack stand if working with the car on a lift.
- Hand tools like wrenches, sockets, ratchets and extensions.
- Harmonic balancer.
- Crankshaft pulley.
- Crank pulley.
- Crankcase pulley.
- Damper or dampener.
- After market crank pulleys designed to increase engine power are called underdrive pulleys.
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