A rough idle is easy to shrug off as a little “quirk” of your vehicle.
Although a rough idle can seem harmless, it is often the first sign of a bigger issue beneath the surface.
How do you recognise a rough idle? What are the causes and solutions?
Find all of your answers below.
What is a rough idle?
When your car is stationary, your engine should idle smoothly at around 1000RPM, and give off a constant even sound.
A rough idle may include any of the following:
Idling below or above its regular speed
Inconsistent RPM
Shaking or vibration through the car
A skipping, slipping sound
What causes a rough idle?
A rough idle can be caused by many different car faults. Below are the four most common.
Dirty Fuel Injector
Modern vehicles are fitted with fuel injection systems, which inject fuel into the cylinders to create a mix of air and fuel to burn. The fuel injector isn’t entirely self-sufficient, and needs some attention from time to time to avoid a build-up of gunk.
A clogged injector will create a lack of fuel in your car’s engine which is similar to giving your body a lack of oxygen – essentially it suffocates your car. It’s no wonder, then, that rough idling can be the result of a clogged fuel injector.
If caught early, this issue can be fixed by simply cleaning your injector. However, when left too long, the system will need to be replaced. The moral of the story – get onto it early!
Vacuum Leak
While modern vehicles use a fuel injector system to burn gas, many older cars use a carburetor to process fuel. As your car rolls along, the engine takes in a mix of air and fuel that allows it to keep moving. This intake relies on a vacuum that is created between the carburetor and the piston tops.
When this vacuum is sealed, your car will run at optimum speed, performance and efficiency. If there is a leak in this vacuum, the ability for your car to gain energy from the burning fuel is compromised, causing rough idling. In the short term, a vacuum leak is a relatively easy fix. Left untouched, a leak can cause some serious problems.
Incorrect Idle Speed
Car engines are usually made to idle at a standard speed of 1000RPM. If your car has a rough idle, it may be because your idle speed setting is incorrect. This setting can be easily reset using a butterknife or similar tool. But keep in mind, the idle speed should be set in stone – if it is inconsistent or changes at random intervals, you may have a bigger issue on your hands.
Damaged or Incorrectly Installed Spark Plugs
Spark plugs create the spark that allows your car to constantly burn fuel. When your spark plugs are failing or incorrectly installed, the engine idle will usually be affected. You may notice vibrations in the car or unhealthy noises – all signs that your engine is struggling to process the fuel it badly needs.
Worried about your car?
Don’t ignore a rough idle. Resolve any lingering issues before they snowball into big problems.
