Common Causes of Rough Idling

Does your car feel rough and jerky when the engine is idling? Known as rough idling, this is an all-too-common problem reported by drivers. The good news is that it's also easily fixed, at least in most cases. The first step to fixing rough idling, however, is to understand what causes it. Here are some of the most common causes of rough idling.

Broken Vacuum Hose

One possible cause of rough idling is a broken vacuum hose. Automotive engines are designed to operate with a specific ratio of air to fuel. When a vacuum hose breaks or is knocked loose, this ratio is thrown off; thus, resulting in performance symptoms like rough idling. Replacing the damaged or affected hose will typically resolve the problem.

Worn Spark Plugs

Another common cause of rough idling is worn spark plugs. In an automotive engine, each cylinder head is given its own dedicated spark plug. These small devices are responsible for creating the ignition needed to ignite the fuel and create combustion. When they become worn, however, that may fail to produce this ignition, or they may fail to produce enough ignition to keep the engine running smoothly when idling.

Refer to your car's owner manual for more information on when and how to change the spark plugs. Normally, though, most automakers recommend changing the spark plugs once every 30,000 to 40,000 miles. If your spark plugs have exceeded this life expectancy, this may be the source of your rough idling.

Dirty Fuel Injectors

A third common cause of rough idling is dirty fuel injectors. Fuel injectors are designed to spray fuel into the cylinders, after which the combination of air and fuel is ignited to create combustion. When fuel injectors become clogged, it restricts the flow of fuel, which can subsequently cause symptoms like rough idling and loss of engine power.

 You can buy and use a fuel injection cleaning additive to clean your fuel injectors. These products are poured directly into your car's gas tank, after which the product will work its way into your injectors to clean them.

Failing Fuel Pump

Finally, a failing fuel pump may cause rough idling. As the name suggests, the fuel pump is designed to pump fuel from the gas tank to the engine. If it fails, your engine won't receive the fuel it needs for proper combustion, which can lead to rough idling.