Why the Car is Idling Rough & 10 Tips to Solve Rough Idle Causes-Part II

Posted by Candy Lai on


Why the Car is Idling Rough & 10 Tips to Solve Rough Idle Causes-Part I, we talked about Top1-5 common causes for rough idling. 


Now, we'll go on the Top-6-10.

6. Aging Engine Mounts

When motor mounts are aging, they can't absorb the vibration during driving or car idling.
Mounts can keep engine stay in proper position to prevent the excess vibration especially when driving thru the rocky bumpy terrain.
Once the motor mounts malfunction, you will feel vibration and noises.
Check-->When to Change Your Motor Mount

7. Faulty EGR Valve
EGR, the Exhaust Gas Recirculation Valve, is responsible for sending exhaust gases back to engine through intake system.
So it can lower the emissions.
EGR valve may stuck in open or closed position and will lead to rough idling symptom.
This is because the fuel-air mixture to cause EGR Valve failure.
Meanwhile, your Check Engine Light will be on to remind you to check if anything wrong with engine.


8. Faulty PCV Valve
Positive Crankcase Ventilation, so called PCV, is to prevent un-burned gases from crankcase and deliver them back to engine again to be burned.
Over time, PCV valve very likely would be filled with dirt & sludge and cause the valve to be blocked and inoperative.
Then, if the valve is starting to leak, it will cause fuel-air mixture then the rough idling appears.
Periodical check and maintenance is the best way to prevent this problem from occurring.
Make sure it is clean regularly!

9. Oxygen Sensor Failure 
Oxygen sensor, part of emission system, is in charge of oxygen content & exhaust gases volume measuring which exit the combustion chamber.
The measuring data will be sent to engine computer to instruct the proper fuel-air balance.
Over time, it will be worn out or covered with carbon deposits.
When oxygen sensor is dirty, it triggers CEL on and causes rough idle.
Fuel efficiency will start to be poor and the emissions test will fail.


10. Vacuum Hose Leak
The engine mixes air and fuel to generate power to keep car rolling.
In between the piston top & carburetor, lying the vacuum that in charge of air & fuel intakes.
If the hose or vacuum itself has any leaks, fuel burning is compromising and will cause rough idling.

So, these are the most common reasons cause our cars idle rough.
If your car is not only idle high, but even stall, that will be another story!

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