Why Is My Vehicle Idling So Rough?

Why Is My Vehicle Idling So Rough?

rough idle, idling rough, vehicle maintenance


So, your car, truck, or van is idling rough… what is the cause? And what can you do to fix it? Even if you aren’t the savviest person when it comes to vehicles, you should know how to identify rough idling.

Rough idling is a common problem, of which the exact cause can be difficult to diagnose, as several factors may come into play. How your engine idles is a good indicator of its overall health; addressing the problem sooner rather than later and checking all potential causes is important.

How To Tell If A Vehicle Is Idling Rough

If your vehicle is experiencing rough idling, you’ll probably know it immediately. While some cases are less severe than others, a rough idle is usually identifiable by a shaking and bouncing sensation in the vehicle.

You may also notice odd sounds, as well as inconsistent RPM counts. Normally, a vehicle should have a smooth and consistent RPM rate of around 1,000. If your vehicle is falling below or rising above this you may be dealing with an idling issue.

Read on to learn a few of the reasons why your engine may have a rough idle, how to identify them and some simple fixes to try.

4 Common Reasons Why Your Engine May Be Idling Rough

1. Vacuum Leak

Most vehicles have a maze of hoses throughout which create a vacuum for both fuel and air. In older engines with a carburetor, this vacuum pulls the fuel into the engine. Most newer vehicles, however, have a throttle to regulate engine speed and airflow through the system. This also creates a vacuum within the intake manifold. These hoses can wear out over time and a leak may develop. If too much air gets mixed in with the fuel, it will cause your engine to misfire. This will result in a rough idle, usually at a higher RPM.

2. Spark Plugs

A rough idling engine can be caused by spark plugs or spark plug wires. Spark plugs use the electrical current received from ignition coils to ignite the air/fuel mixture within the combustion chamber. A plug that is damaged or installed incorrectly can result in fuel being burned at an inconsistent rate. If the damage is bad enough, you may also notice your engine running rough while driving. Pay attention to any jerks or stutters, particularly while accelerating under a load, as a symptom.

3. Dirty Fuel Injector

Sometime dirty parts can also be the root cause of a rough idling engine. Fuel injectors disperse fuel into your vehicle’s engine at a precise angle and quantity, to ensure optimal performance. That being said, dirty fuel injectors are also a major contributor to poor gas mileage. Using an injector cleaner gas additive, such as Berryman B12 Chemtool, is a simple way to prevent this problem and keep your engine running smoothly and efficiently.

4. Carburetor Problems

Older vehicles utilize a carburetor rather than a fuel injector. Black exhaust smoke is a common indicator of a problem with the carburetor. A carbureted system that is running well shouldn’t produce excessive amounts of black smoke, so look out for this as a sign that something is wrong. Using a carburetor cleaner is a simple step to help dissolve these carbon deposits and keep them clean in order to prevent or decrease a current rough idle.

An engine which is operating properly should run smooth without any excess noise. If it begins to idle ‘rough,’ there are a number of possible causes. How your engine idles is a good indicator it its overall health; addressing the problem sooner rather than later and checking all potential causes is important. If you’re unsure what the problem is, it is always a good idea to call in the professionals for a diagnosis. The underlying issue can also affect your vehicle’s overall performance in the long term, meaning it’s a good idea to get it resolved as fast as possible.


At Berryman, we are committed to providing prompt personal service and producing products that meet the highest quality standards of performance, reliability and environmental responsibility. For accurate information and quality products you need to handle rough idling and other vehicle issues, contact us today!

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