Rough Idle in Cars – Causes, Indications and Solutions

Rough Idle in Cars – Causes, Indications and Solutions

Rough idle is a term that is used to describe the problem with a car’s engine. It happens when your car is not moving but running. You hear some strange noises and vibrations. This can happen because of differnt reasons such as spark plugs, Clogged Air Filters, fuel, Vacuum Leaks, air getting into the engine, Faulty EGR valves, and many others.

In the below blog, let’s discuss the causes of rough idling and learn the process of how to fix them.

What are the Indications of Rough Idle?

Here are some of the symptoms that you need to know about rough Idling.

  • Slow Acceleration
  • Reduced Fuel Economy
  • Air System
  • Shaking
  • Unusual Noises
  • Difficulty Starting your Vehicle
  • Motor Mounts
  • Engine Stalling
  • Lack of Power or Sputtering
  • Spark Plugs

Causes of Rough Idling:

Here are some of the possible reasons that cause the rough idle. Let’s have a look at them.

Dirty Fuel Injector:

Fuel is injected into the engine by fuel injectors. Due to Contaminants, the fuel injector gets dirty. It doesn’t supply fuel and doesn’t function as well as the engine. Rough idling is caused by an imbalance between the fuel and air levels.

Faulty Oxygen Sensor:

It monitors the amount of oxygen in the vehicle’s system as well as the exhaust gases released through the exhaust pipe. Additionally, it supports the proper air-to-fuel ratio from heating as well as maintenance and control of your car’s module. The air-fuel mixture and engine speed could be greatly affected by a damaged oxygen sensor.

 Faulty EGR Valve:

EGR valves are used to regulate emissions. It guarantees that exhaust gases enter the intake manifold and lowers engine emissions. However, the EGR Valve shouldn’t run while the engine is idle or with the throttle wide accessible.

Faulty EGR Valve

Dirty Throttle Position Sensor:

The throttle position sensor measures the position and performance of the throttle plates. It is also very useful for assisting the ECM, controlling the fuel-air mixture, and ignition timing. It regulates the quantity of air that enters the engine. If it becomes blocked or dirty. Then, it causes the engine to run stall or roughly.

Dirty or Clogged Air Filter:

The filter keeps dirt and debris out of the engine. Your air filter can eventually become clogged, preventing air from entering the engine. It can restrict airflow to the engine if it gets clogged or dirty, which can cause rough idling and stalling. Ensuring the smooth operation of the engine requires routine maintenance.

Vacuum Leaks:

There are several vacuum hoses in your car engine, and they can break over time and cause leaks. When air gets into the engine through a crack or hole in the vacuum system, there is a vacuum leak. This may result in the engine running richly or lean, which would lead to rough idling or stalling.

Clogged Fuel Filter:

The fuel filter screens out contaminants from the fuel before it reaches the engine. If it gets clogged, the engine may have less fuel flow, which could result in rough idling and stalling.

Faulty PCV Valve:

It is crucial in directing unburned gases from the combustion chamber into the engine so they can burn all the way through. However, due to its ongoing exposure to stressors and pollutants like mud or dirt. Over time, the valve may become clogged. It may leak if it becomes clogged, producing a lean air-fuel mixture and a rough idle.

Faulty PCV Valve

Faulty Ignition System:

The engine may misfire, stall, or operate rough due to an issue with the ignition system, such as defective spark plugs, distributor, or ignition coils. On the other hand, maintaining the best engine performance greatly benefits from the ignition coil. Additionally, it ignites the fuel-air mixture when used together with the spark plugs.

 Malfunctioning Idle Control Valve:

The amount of air that enters the engine while it is idling is controlled by the idle control valve. It may cause the engine to stall and run rough if it is dirty or malfunctioning.

 Engine Sensors:

The throttle position sensor, oxygen sensor, and mess airflow sensor are just a few of the sensors that are installed in these modern cars to track engine performance. It is unlikely that a malfunctioning or failure of one of these sensors will result in rough idling installation.

 Faulty Spark Plugs:

It frequently occurs as a result of a misfire caused by faulty spark plugs. Its purpose is to ignite the air-fuel mixture by creating a spark. If they are damaged or there is corrosion in the spark plug wires. Incorrect ignition timing may come from it. There will be an error in the ignition timing. This may cause a misfire, stutter, or rough idle.

 IAC Valve:

The amount of air that enters the engine during rough idle is controlled by the idle air control valve. It may cause rough idling when this valve clogs and malfunctions affecting the idle airflow.

 Bad MAF Sensor:

The engine’s air intake is measured to establish the proper fuel-air mixture for fire. The engine’s air-fuel ratio could be seriously affected by a malfunctioning mass sensor. You must replace your MAF sensor as soon as possible if it is damaged.

Bad MAF Sensor

How to Fix Car Engine Idle Problems?

Follow the process and learn all about the fixing of car engine idle problems.

  • Use a spray named “Throttle Body & Air Intake Cleaner”. Deposit often builds up in the throttle body while you need to clean them out.
  • The first thing you need to do is remove the housing and air filter and all the ductwork that’s in the way.
  • Unsnap the air filter container and pull it up.
  • Now, get a screwdriver and loosen all the clamps on the ductwork.
  • Then, pull the assembly out of the way. After that pull off the last two pieces of ductwork and the throttle’s inside.
  • Get the spray throttle cleaner and spray the throttle plates.
  • Open the throttle with one hand and spray them with your other hand.
  • Now, get a clean paper towel, spray it with some more, and wipe all the curd off.

How to Clean the Car Idle Air Control Valve?

Let’s have a look at the process of cleaning your car’s idle air control valve. Follow the steps and learn about it.

  • Take the screws and hold it in place.
  • Take the assembly off to clean the inside of it.
  • Spray all around the cleaner. Make sure that all the holes are clean.
  • Make sure that all the holes are clean. So, there’s no carbon left.

Note: Let the car in the air dry for about half or 1 hour before you put it back together and start the car. Otherwise, the car will be full of cleaner is very hard to start. Then, put all the air duct housing back and put the clip back on the air filter.

Frequently Asked Questions:

Q. Why is my car stuttering at Idle?

There are several reasons for car stuttering such as

  • Accumulation of Moisture
  • Dirty Fuel Injectors
  • Blocked Catalytic Converter
  • Damaged Fuel Pump
  • Broken Spark Plugs
  • Faulty Mass Airflow Sensor

Q. How do you reduce rough idle?

You can reduce rough idling after performing regular maintenance. If you see any of the faults and symptoms then you can check out. Check the problem and solve it. If you think that the problem still does not resolve, take your car to the car manufacturer.

Q. Why does my car shake at Idle but smooth out while driving?

It happens because of

  • Bad spark plugs
  • Loose battery cables
  • Loose gas cap
  • Damaged engine mount
  • Worn throttle sensor


I Hope after reading the above blog about rough idling, you will come to know all about its possible causes. You can check all the symptoms of rough idle. Moreover, you can also check how you can fix these rough idling problems. However, after you fix them, if the problem still persists, then you have to take a recommendation from the car manufacturer.

Zeeshan Tahir

Hi, This is M. Zeeshan Tahir, Junior Editor at since july 2023. I am Expert in research of Updating data regarding media Industry and Business Niche. I always rooming to find out latest happenings in this Industry to write for our users. Our users requirement is our 1st preference. Researched and Proper Structured data is our Value. If any one find out any doubt in any news or blog post must reach out to us. Our Editorial Team will Check it. Thanks!

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