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Car Idling Rough

Car Idling Rough

Cylinder Misfire


When the engine runs rough at idle it means that rough idle causes the engine misfiring in one or more cylinders.

The reason why car idling rough
(1) Engine misfiring in one or more cylinders

An engine that runs rough while idling indicates that one or more of its cylinders is misfiring. This is simply because misfiring cylinders disrupt an engine's natural balance. Now, you are probably wondering what specifically causes a cylinder to misfire? Well, there are many, many possibilities but unfortunately, none are very easy to test for. This is why the above (very general) diagnosis was suggested.

Incidentally, two common causes of cylinder misfire are

1) a vacuum leak, and
2) bad spark plugs or spark plug wires.

Additionally, if the vehicle is equipped with fuel injection, it is possible that one or more fuel injectors could be clogged. This will create a "fuel-starved" condition in the corresponding cylinders and thus misfiring.


What to do?
You might try replacing the spark plugs and spark plug wires. This is a procedure you can do yourself and it may solve this rough idle problem. However, if it doesn't or you don't feel too comfortable doing this, you will need to take this vehicle to a garage for complete analysis and repair. Such garages tend to be reputable and, best of all, if you have a dispute after any work is done.

How to Replace Spark Plug


Related Topic:

Car Shaking While Idle

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Engine Pinging Noise While Driving

Engine Pinging Noise While Driving

When the car makes pinging noise while driving, the noise usually indicates a problem related to the engine. However, there are other cause like the use of cheap low octane gasoline or may also cause by driving the car in high altitude area.

Reasons why engine makes pinging noise while driving

(1) Use of low octane gasoline
(2) Driving at high altitude area
(3) Engine related problem

Use of low octane gasoline
Low grade or "cheap" gas is generally considered to be gas with an octane rating of 88 or below. The bad thing about low-grade gas is that it burns too easily. Put another way, low-grade gas is too combustible. You see, the gas that burns too easily will, under certain conditions, self-ignite before the piston reaches the top of the combustion chamber... this is known as pre-ignition. When pre-ignition occurs, you'll hear a pinging sound.

Engine Pinging Noise While Driving

Generally, pre-ignition only occurs under conditions such as when the engine is under stress and/or really hot. When driving up a hill, the engine is under stress. This stress will trigger pre-ignition (and thus pinging).

What to do?
Use higher octane gasoline. High octane fuels have a rating of 92 or above and are usually called "Super" gasoline. Incidentally, the octane rating is displayed on the front of the gas pump.



Driving at high altitude area
If the only time the engine makes a pinging sound is on high altitude roads. What is significant about high altitude roads is the fact that the air is thin. Now, when an engine is both under stress (e.g. driving up a hill) and it has only thin air for combustion, the fuel will tend to ignite in the combustion chambers before it is should. This condition is known as "pre-ignition". When pre-ignition occurs, a pinging sound results.

Engine Pinging Noise While Driving

What to do?
Try using high octane gasoline the next time you anticipate driving on high altitude roads. High octane fuels burn slower and are therefore more resistant to pre-ignition. If pre-ignition is eliminated, pinging is eliminated as well. High octane fuels have a rating of 92 or above and are called "Super" gasoline. By the way, the octane rating is easy to determine... it's displayed on the front of any gas pump.

Engine related problem
If the car has fuel injection. Fuel-injected engines have a gadget called a "load sensor". The purpose of this sensor is to measure the load/stress on the engine. When the load is high, such as when driving up a hill, the load sensor (if working) will send a signal to the engine's control unit to indicate a "high load" condition. Based on this signal, the control unit makes a calculation and uses the result to adjust the engine's operation so as to avoid pinging. Clearly then, if the load sensor isn't working, the engine will probably ping when driving up a hill. From the above, you may be thinking that the control unit could be faulty and not the load sensor.  Although this is possible, it's rare.  Further, if the control unit was faulty, the engine would probably not run at all.

What to do?
Take the car to a car repair shop and have the mechanic check the load sensor.  If it is indeed faulty, have it replaced. When talking to the mechanic, try to describe the nature of this problem just as described in this article. Don't ignore this pinging sound.  Pinging is actually an indication of something called pre-ignition.  When left uncorrected, pinging/pre-ignition can ruin an engine. If you aren't currently using "Super" gas, try a tank. Super gas is formulated to resist pinging and thus can act as a temporary fix to this problem.

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Car Shaking While Idle

When a car is shaking while idle, it means that the engine is misfiring in one or more cylinders.

Car Shakes While Idle

Engine Cylinder


Reasons why the car is shaking while idle

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Honda Civic Won’t Start Makes Clicking Noise

Honda Civic Won’t Start

Does your Honda Civic won’t start, makes clicking noise during starting? Since the engine is not starting there are two possible reasons why your honda civic is not starting, clicking noise that is heard during starting is because of the solenoid from the stater. The solenoid is the one that allows the current from the battery to flow into the starter to make the engine crank. With that said the possible cause of the problem is a weak battery or the starter is failing.

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