Car Idling Rough

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Car Idling Rough

Car Idling Rough

When the engine runs rough at idle it means that rough idle causes the engine misfiring in one or more cylinders.

The reason why car idling rough

(1) Engine misfiring in one or more cylinders


An engine that runs rough while idling indicates that one or more of its cylinders is misfiring. This is simply because misfiring cylinders disrupt an engine's natural balance. Now, you are probably wondering what specifically causes a cylinder to misfire? Well, there are many, many possibilities but unfortunately, none are very easy to test for. This is why the above (very general) diagnosis was suggested.

Two common causes of cylinder misfire are:

1) a vacuum leak, and
2) bad spark plugs or spark plug wires.


Additionally, if the vehicle is equipped with fuel injection, it is possible that one or more fuel injectors could be clogged. This will create a "fuel-starved" condition in the corresponding cylinders and thus misfiring.

Fuel injector cause of misfiring

What to do if the car is idling rough?

You might try replacing the spark plugs and spark plug wires. This is a procedure you can do yourself and it may solve this rough idle problem. However, if it doesn't or you don't feel too comfortable doing this, you will need to take this vehicle to a garage for complete analysis and repair. Such garages tend to be reputable and, best of all, if you have a dispute after any work is done.

How to Replace Spark Plug


Engine Diagnostic
Engine diagnostic guide for car engines common problem from a technician experience, this will serve as a guide to solve your common engine problem, please feel free to read out the engine diagnostic articles.
Learn more: Engine Diagnostic

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