Can a Bad Battery Cause Rough Idle? (Explained)

A car battery is one of the important parts of a car’s internal system. Car batteries are rechargeable and they supply electric current to the starting motor. The starting motor then helps the engine to start the car with an electric current that is supplied by the battery. 

Today, we are going to discuss whether a bad battery can cause rough idle or not.

Can a bad battery cause rough idle?

A battery can certainly cause rough idle when it becomes bad. The car battery supplies much-needed electrical power to the fuel pump. The fuel pump is unable to provide enough fuel to the car engine when the car battery becomes bad. It can go bad if there is corrosion on the battery terminals. 

Many things can be responsible when your car engine starts to rough idle. But a bad car battery definitely has the skillset or lack of it to cause your car rough idling. The car battery is critical for the car engine as it provides much-needed power to the fuel injector.

A bad car battery is not able to supply enough electric current to the fuel injector and the car engine does not receive enough fuel as a result. A battery can become bad in several ways. The battery terminals can become loose or develop corrosion. 

The battery can also become bad by leaking fluids and running out of juice.

A battery usually stays good for about five years. It can become faulty before that too. A faulty car battery causes several problems including rough idling as it provides electric current to different components of the car. 

When a car battery becomes bad, the car alternator has to handle more pressure than usual which causes the car engine to rough idle.

How does a bad battery cause rough idle?

A battery is responsible for providing current to the starting motor. The starting motor works with the engine to start the car. If a battery becomes bad or faulty, then it is not able to supply the required current to the starting motor. 

As a result, the starting motor and the engine can not coordinate together to start the car. This causes the engine to rough idle.

You will feel a shaking sensation coming from your engine when your engine starts rough idling. A car battery can go bad for several reasons. It can go bad if the terminals and cables of the car battery are broken, corroded, or loose. 

A bad car battery fails to send enough current to the fuel pump.

When the fuel pump does not receive the required current, it can not supply fuel into the car engine. This causes the air-fuel mixture in the engine to become lean. The engine cylinders misfire as a consequence and the engine starts to rough idle.

Can a loose battery terminal cause rough idle?

Terminals of a car battery can become loose if you drive your car through rough and tough roads. A loose battery terminal can cause a car engine to rough idle. When the terminal becomes loose, the battery is not able to provide current to the starting motor. 

This creates extra pressure on the car alternator to start the engine.

When the alternator fails to handle the extra pressure, the car engine starts to rough idle. The loose battery terminal can be solved easily by tightening the terminal screws with a wrench.

Can corroded battery terminals cause rough idle?

Corroded battery terminals can cause rough idle. 

Battery terminals can become corroded if the corrosion-making fluid and gasses from inside the battery start leaking. The leaked fluid and gasses cause corrosion on the battery terminals through chemical reactions.

When the battery terminals become corroded, it fails to supply enough power to the fuel pump. As a result, the fuel pump sometimes fails to supply the required fuel into the engine causing it to rough idle. 

The white corrosion on the battery terminals can be wiped away with a stainless steel wire brush. Anti-corrosion grease can also be applied to the battery terminals to stop them from becoming corroded.

Can an old battery cause rough idle?

An old battery can cause rough idle. A car battery is expected to last for four years in most cases. It can go bad before four years too. As the car battery becomes older, it loses its effectiveness gradually. You will see an alarming amount of corrosion on old car batteries. 

You will also notice the old car battery leaking fluid and gasses.

When a car battery becomes old, the transfer of power from the battery to the fuel pump is interrupted on a regular basis. This interruption causes the car engine to rough idle because it does not receive enough fuel from the fuel pump and the air-fuel mixture becomes too lean.

Can a weak battery cause a car to run rough?

A weak battery puts too much pressure on the car alternator. When a car battery continuously fails to deliver the required power to the fuel injector, then the car alternator needs to step in. The car alternator sometimes needs to recharge the weak battery to keep it alive.

This continuous failure of a weak battery makes it difficult for the engine to perform at the optimum level. One or multiple cylinders of the engine misfire as a consequence causing the car to run rough. So a weak battery causes a car to run rough.

What are the signs of a bad battery in a car?

When a car battery becomes bad or faulty, it will start showing several signs and symptoms. Let’s discuss in detail the signs of a bad battery in a car.

Engine Misfire:

If a battery becomes bad, then it will not be able to provide enough power to the fuel injector. The engine will not receive adequate fuel as a result. This will cause a misfire in one or multiple cylinders of the engine.

Rough idle:

The air-fuel mixture of the car engine becomes too lean when the car battery becomes bad. It causes difficulty while starting the car. You will get a shaky feeling from the car when the battery becomes bad and causes the car to rough idle.

Check engine light:

If your car battery becomes bad, the check engine light will turn on. Although it can indicate other problems. But you should run a battery error code to find if your battery has become bad.

Corrosion:

A bad battery will have white corrosion on its terminal. The white corrosion indicates at fluid and gas leakage from the battery.

Failure of electrical components:

A car battery is responsible for providing electrical current to the important electrical components of a car. When a car battery becomes bad, it is not able to supply current to these components. 

As a result, these electrical components fail to operate at the optimum level causing all sorts of problems.

Rotten smell:

A car battery will emit a rotten smell similar to a rotten egg when it becomes bad. If this rotten smell coincides with any of the signs above, then you should immediately get your car battery checked by a mechanic.

Can I drive with a bad car battery?

You can not drive with a bad car battery for a long time. The car battery coordinates many critical parts of your car. If the battery becomes faulty or bad, the entire internal system of your car will come to a halt. 

When your car battery becomes bad, the car engine will start to rough idle initially. But eventually, the car engine will fail to start leaving you stranded on the road.

When you sense that the car battery has gone bad, you should take your car to a mechanic or repair shop immediately. Driving around with a bad car battery will only delay the inevitable and increase the maintenance cost of the car by damaging the other parts too.

How do you know when a car battery needs replacing?

A car battery gives reliable service for up to four years. If you take adequate care of your car battery, then it can stay good for five years at the very most. After that, the car battery starts acting up causing all sorts of problems. 

When you notice that there is a significant amount of white corrosion on your battery terminal, then the time for a new battery has come.

You will also face difficulty while starting your engine if the car battery becomes bad. You should not delay replacing the car battery when it starts causing problems. A bad battery will only increase the damage if it is not replaced in time.

Final Thoughts

A bad battery can cause the car engine rough idling. If the battery terminal is loose or corroded, then the battery becomes bad. It is not safe to drive around with a bad car battery as it can severely damage the engine and other parts of the car. A car battery stays good for four or five years.