If your car runs rough idle, your engine may vibrate, or wobble while it is running. As a result, your overall driving experience feels rough and you are likely to bounce off it a bit in your seat.

When the engine is idling, there is usually a misfire that you can only feel by holding onto the steering wheel. In addition, the idle speed of your engine is higher than normal. The speed normally returns to normal when you accelerate the vehicle, but increases again after stopping. This is definitely not a normal situation.

If you have a rough idle or your speed is high, there are several reasons why this could happen. It is not always easy to diagnose the cause because there are so many factors involved.

Below are the top 5 causes a mechanic would look for:

1.
Bad spark plugs

If you have bad spark plugs because they are worn or damaged, this can cause your engine to idle. Remember that spark plugs conduct electricity into the combustion chamber to ignite the fuel and air mixture.

If the spark plugs are defective, the electrical current is insufficient for the ignition. As a result, the fuel-air mixture burns inconsistently, which leads to a rough idling of the engine.

2.
Vacuum leak

There are many hoses that help deliver both fuel and air into the combustion chamber. A very common cause of rough idling is a problem with a vacuum hose in the vehicle. The hose can be damaged, loose, or worn and causes a leak.This could cause a lot of air to mix with the gasoline, which would cause misfires. The result would be a car that is rough when idling or has a higher engine speed than normal.

3.
Malfunctioning Caburetor

Carburetors were previously used in vehicles before the injectors were invented. Maybe you have a vehicle with a carburetor.
In this case, the carburetor itself can have problems that causes the engine to run rough. A warning sign would be if your exhaust smoke turns black.

4.
Dirty fuel injector

Injectors are the modernized way vehicles deliver fuel to the combustion chamber. The only thing is that these injectors can get dirty or clogged after a while.

If you don't use gas additives or injector cleaner regularly, there is a good chance that you will eventually get a dirty injector. This causes your car to run badly at idle.

5.
Clogged air filter

The engine needs air from outside to mix with the fuel in the combustion chamber. There is an air filter that prevents dirt from the air from entering the chamber.

However, if this air filter is dirty or clogged, less clean air will flow through it. This causes the engine to idle.

FINAL WORDS
The cost of repair depends on the cause. If you take your vehicle to a repair shop soon, your engine should be fine.

However, if you leave the engine idling for too long, the engine can be irreversibly damaged. This, in turn, could cost you a lot of money. So don't wait for it.
Source:
https://www.eliancars.com/2020/02/5-causes-of-rough-idling-or-high-speed.html
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