Idle Misfire Vibration

The engine in your car is designed to run balanced to minimize vibration to the passengers. Vibration is the most noticeable when the engine is at an idle. Several components are designed to help minimize engine vibration. We have listed some of the most common problems and repairs below.

Car Repair Troubleshooting Guide

Check for Vacuum Leaks - An engine depends on vacuum to operate correctly, check the engine for vacuum leaks.

Intake Valve Test - An intake valve must be seal completely or intake gases will contaminate the intake charge causing the engine to idle rough.

Checking Engine Mounts - Engine mounts are used to minimize engine vibration by isolating the engine from the car frame. These mounts are constructed by using rubber vulcanized between to metal plates with threaded studs that bolt to the engine and the frame of the car. When motor mounts become worn they allow the engine the contact the frame causing a noticeable vibration. Inspect the engine mounts for integrity, look for any oil, cracks or separation of the mount. Remove the failed engine mount and replace if needed. For exact instructions how to replace the engine mounts in your vehicle consult an auto repair manual.

Engine Mount
New Engine Mount (appearance will vary)

Inspecting Balance Shaft Timing - A balance shaft belt is used inside some designs of engines to counter act vibration created by the natural engine operation. Many balance shafts are operated by a timing belt that can break or become out of correlation with the engine either by a worn timing belt or misalignment when replaced. To inspect for this problem, remove the timing belt cover and inspect timing belt marks for proper alignment. All engines are different, consult a repair manual for exact belt alignment specifications.

Testing Engine Compression - An engine depends on an equal compression reading in each cylinder. If poor compression exits in one or more cylinders it can cause a rough idle condition. To check for this condition perform an engine compression test to compare readings. Once a low cylinder has been detected addition internal engine inspection is required.

If further assistance is needed, our certified car repair technicians are ready to answer your car questions.

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Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2013-10-12)