11 Common Causes of Rough Idle | How To Fix Car Rough Idling

What is Rough Idle?
Rough idling or rough idle represents the irregular or uneven operation of the engine when your vehicle is in idle mode or at a standstill. Instead of running efficiently, your engine may produce different signs, such as unusual noises, vibrating, or shaking. Rough idling is one of the clear symptoms of an underlying issue with the engine or its components.
Causes of Rough Idle
1) Faulty PCV Valve
The PCV valve of your vehicle plays a crucial role in redirecting unburned gases from the combustion chamber back into the engine to burn completely. However, due to its constant exposure to stress and contaminants like dirt or mud, the valve can be clogged over time. When it clogs, it may produce a leak, causing a lean air-fuel mixture and resulting in a rough idle.
2) Dirty Fuel Injectors
The fuel injectors in your car are responsible for injecting fuel to the engine. As the fuel injector gets dirty due to contaminants, it doesn’t work efficiently and doesn’t supply fuel according to engine requirements.
3) Vacuum Leaks
Your vehicle engine contains multiple vacuum hoses that can wear out and develop cracks over time, leading to leaks. These leaks disrupt the air-fuel mixture and force the mixture to become lean.
4) Bad Ignition Coil
The ignition coil is essential to maintaining proper engine performance. It works in conjunction with the spark plugs to ignite the fuel-air mixture.
5) Faulty EGR Valve
The EGR valve ensures the entry of the exhaust gases to the intake manifold and reduces the emissions from the engine. As it goes bad, it can stick open and result in a rough idle or, in more severe cases, cause the engine to stall.
6) Faulty Spark Plugs
A rough idling engine often occurs due to a misfire caused by defective spark plugs. A spark plug is used to produce a spark to ignite the air-fuel mixture.
As the spark plug is damaged or if there is corrosion in the spark plug wire, it can result in improper ignition timing, the ignition timing will be off. This, in turn, causes the engine to idle roughly, stutter, or misfire.
7) Clogged Air Filter
The air filter plays a critical role in maintaining proper engine operation by preventing contaminants from entering the engine. Over time, your air filter can be clogged, preventing the air from entering the engine.
8) Faulty Oxygen Sensor
The oxygen sensor is one of the major components of the car's emissions system. It measures the oxygen level in the exhaust gases emitted from the exhaust pipe.
However, a damaged or malfunctioning oxygen sensor may badly affect the air-fuel mixture and engine speed.
9) Bad Throttle Position Sensor
The throttle position sensor monitors the position and performance of the throttle plate. It plays a crucial role in assisting the ECM in regulating the fuel-air mixture and ignition timing. However, a defective throttle position sensor may disrupt the ignition timing, resulting in a rough idle.
10) Bad Idle Air Control Valve
The idle air control valve is used to regulate the amount of air entering the engine during idle. When this valve fails, or becomes dirty, it may disturb the idle airflow, causing rough idling.
11) Bad MAF Sensor
The MAF sensor is used to measure the amount of air entering the engine to determine the appropriate fuel-air mixture for combustion. A bad MAF sensor may badly affect the air-fuel ratio in the engine, causing rough idling.
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Disclaimer:
This video is just for educational purposes only. We are not in the auto repair business nor publish automotive service manuals. This video is not reviewed or authorized by any vehicle manufacturer. This video is intended only as general guidance. Every system is slightly different, so refer to the owner’s manual of your vehicle for any specific information about your model. Remember that only proper service and repair procedures will ensure your car's safe and reliable operation.
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[@marccoulson8997]

Why is he putting in a timing chain when talking about a faulty coil?

[@Rick-Sosa]

Which of these would not cause an engine light on?

[@MechanicalBoost]

Kindly elaborate your question

[@gynell2043]

I don't know if I'm having the same issue in relation to his question, but I personally have a rough idle in my 03 GMC Envoy but the engine light isn't on. What issue(s) can cause a rough idle without the engine light coming on?

[@MechanicalBoost]

@@gynell2043 kindly watch the complete video. I already have explained all the issues that may cause rough idle without triggering the engine light. Poor quality Fuel, Defective airflow sensor, Vacuum leaks, bad EGR valve, Bad spark plugs or Low fuel pressure may also cause rough idle without check engine light

[@jackarmando]

@@gynell2043 and make sure there even is a check engine lights, some people remove them just before they sell the car ;)