Can A Weak Battery Cause A Car To Run Rough?

Can A Weak Battery Cause A Car To Run Rough?

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Can A Weak Battery Cause A Car To Run Rough?

We have already seen that one effect of a weak battery is a rough idle.

However, since many other factors cause a rough idle, you might never be sure until it’s tested for ascertaining.

Many people understand that a weak battery causes poor engine performance. But when it comes to rough idling, the numbers dwindle.

Yes, If you have a weak battery and the alternator isn’t charging the battery as it should, you will experience rough idling. The sudden demand on a weak battery will cause your car to experience rough idling. Still, the condition can be aggravated by turning on the headlights.

And to be sure that you are dealing with a bad battery, let a professional check your battery and alternator.

A faulty alternator will not charge the battery, making it drain or even die.

If you go ahead and replace the battery, you might discover that the problem persists, meaning that you have addressed the wrong thing.

While many problems will contribute to your car not running correctly, a weak battery will not only cause rough idling but other problems like not starting and probably stalling.

Can A Weak Battery Cause A Misfire?

It depends, but at least, it will not happen directly. It’s common for a car whose battery is weak to run rough. It’s not easy for a car to idle if it has a weak battery:

It simply can’t sustain a smooth idle. Indeed, a weak battery will cause some engines to stall every time, but others will be lucky enough to stall occasionally.

As you might know, your car’s battery(Amazon Link) is the part your alternator relies on to produce power for running the engine.

Consequently, having a weak battery makes it hard, if not impossible, for the alternator to carry out its functions. Additionally, there will be a decline in the performance of your car.

Although there are many signs that your car has a weak battery, the worst among them are misfires. The easiest way to identify a misfire is to feel that your engine is running rough.

Misfires come as a result of incomplete combustion in the engine cylinders. The cylinders might be one or more.

When your engine misfires, you will feel as if the car is shaking as your engine runs. A weak battery will affect the fuel pump, causing an engine to misfire.

Low juice coming from the battery makes the fuel pump not work at the speed required.

What Problems Can A Weak Car Battery Cause?

There are several problems that a weak car battery will cause. But before I discuss them, it is important to briefly mention the functions of a car battery.

The‌ ‌car‌ ‌battery‌ acts as the source of the‌ ‌necessary‌ ‌electricity‌ for powering all ‌the‌ ‌electrical‌ ‌components‌ ‌in‌ ‌your‌ ‌vehicle.‌ ‌

You will not have electrical components working if you don’t have adequate electrical power.

Components that will take the toll include ‌the‌ ‌dashboard‌ ‌lights,‌ ‌headlights, or‌ ‌power‌ ‌windows.‌

Therefore, if you notice that you lack the necessary ability to power accessories at the right level, look for weak car battery symptoms. ‌ ‌

If you notice that the headlights are mostly dim, hardly getting any brighter even after revving the engine, your battery might be weak.

Again, a weak battery will produce a clicking sound when you turn on the ignition key. The electrical current will be sent to the starter solenoid to power up the vehicle.

However, a weak battery will not get any signal to the solenoid so that the starter won’t start the car.

But one of the damning effects of a weak battery is damaging the alternator.

You might have other symptoms like slow cranking, a faulty crankshaft position sensor, a damaged fuel system, and a broken engine control unit.

Can Bad Battery Ground Cause Misfire?

Yes, but indirectly. If you have a bad battery ground, it means that enough voltage does not get to the necessary parts.

For instance, there will be a loss of spark since coil voltage will not effectively jump from the electrode gap at the spark plug’s end.

A bad battery ground can cause issues on all electrical components. And as you might be aware, a weak spark will cause misfires.

Therefore, if you have a faulty battery ground, it’s best to have it fixed without taking too long for that to be done.

With engine misfires, you will have issues with a loss of power when driving. There will be an uneven rotation of the internal engine components.

This will dictate untimely wear and tear that is not cheap to repair. And when you have misfires, you are most likely going to have problems with emissions.

Can A Weak Battery Affect Engine Performance?

Yes, A weak battery can affect engine performance and reduce fuel economy.

Suppose you are oblivious of the effect of a dying battery on your car’s engine and how the performance can be impeded.

In that case, you might wrongly misdiagnose a weak battery for a malfunctioning engine.

When your battery has a lower voltage, this will lead to higher amps and, consequently, higher temperatures. There might be some wear occasioned on the internals. 

Since the alternator works on-demand, it will work harder when low battery.

And because things like your power windows, fuel pump, seats, heaters, dashboard lights, windshield wipers all work off the battery.

you should expect decreased performance if your battery is weak.

But you might never really know the seriousness of the matter until your fuel pump is handcuffed, making your car sputter when idle.

Consequently, you will want to replace a dying battery soon enough before its effects can be felt seriously on the car’s performance.

In addition to poor engine performance, some of the other parts that will register decreased performance include injectors, spark plugs, and electric steering.

But we must not forget that older cars will run perfectly well even without a battery! Indeed, if you jumpstart it, it can run the whole day even after disconnecting the battery.

So we must never confuse modern cars fitted with a computer and those old models that didn’t have any ECU.

Can A Bad Battery Cause My Car To Shake?

Yes. A bad battery will cause many problems, one of which is your car shaking. With a bad battery, your alternator must devise a way of compensating for the power deficit.

And this is by way of working harder. No, this is not good for the car as it results in the engine’s unsteady or unsmooth running.

When your engine is not running smoothly, the car will take a toll, and you will feel the car shaking.

So, as long as the battery is not putting out enough power, you should expect to see the car’s smooth running impact. But you also know the car might even stall altogether.

With a bad battery, your car will scarcely accelerate smoothly as it will have issues with hesitation, resulting in a shaky drive or take-off.

It’s good to know that a bad battery might overwork the charging system, causing instability issues, depending on how bad the battery is.

A common denominator in all these is the fuel pump that must get enough electrical power supply to execute its important mandate.

And if it can’t get enough power supply from the battery, the injectors will not get enough to open when commanded to deliver the needed amount of fuel.

Can A Weak Battery Cause A Weak Spark?

Yes, a weak spark will be caused by anything that hinders coil voltage from jumping the electrode gap found the spark plug’s end.

This includes a weak battery, fouled or damaged spark plugs, a cracked distributor cap, or bad plug wires.

A weak car battery will lead to “lean fuel” and improper opening of fuel injectors. When you have these conditions, it’s a recipe for weak sparks, which will lead to misfires.

It’s a whole lot of interconnectedness of all these parts. Therefore#, one part fails, many other parts want to function as they should.

Because weak spark or no spark means no ignition, it is advisable to ensure that the sparks remain at optimal functionality.

So you will want to test your spark every other time to be sure. To do this, insert a spark plug tester or an old spark plug after removing a plug wire.

After this, you will need to place the spark plug tester on the ground or top of a metal surface and then crank the engine, checking for a spark.

But in all these, you want to be careful since a bad ground will still cause a weak spark. Still, a bad stator will also cause a weak spark, so you need to be sure.

What Do I Do If My Car Battery Is Weak?

If your car battery is weak, you might not have many options to replace it. But before you rush to the next auto shop to buy a replacement battery, it’s best to be sure.

Many people have bought new batteries only to discover that their battery was not the problem but a different component like an alternator.

If you wake up and want to rush to the office after a quick breakfast, it is frustrating to hear a clicking sound when you turn on the ignition.

While it might be the battery, you cant be sure. But if you have a multimeter with you, you might be able to check your battery.

But this will only tell you if your battery is fully charged or not.

You will need safety glasses, a digital millimeter, and protective gloves to test your battery thoroughly. First, find the battery by locating it in the hood.

Depending on your car, you will find it near the fender or under the back seat. After you find it, turn off the ignition and the lights, your materials ready.

Now, touching the red multimeter lead to the battery’s positive terminal, and the black multimeter leads to the negative battery cable.

But even if you swap the leads, all you will get will be a negative reading but accurate. Your meter needs to be turned to the DC volts setting (with a line above it).

The difference between this and the DC with the squiggly thing is that the latter is AC voltage. If the battery shows 12.66 volts, it’s fully charged.

If it reads 12.45 volts, it’s 75% charged. A half charge will represent 12.24 volts, while 12.06 volts means 25% charged. Most importantly, if it reads 11.89 volts, it’s 0% charged

Can A Weak Battery Damage An Alternator?

Yes, A weak battery will most certainly cause a related alternator failure, so periodic battery testing as your battery gets older is a recognizable desired preventive maintenance practice.

This type of check is a sure way to steer away from alternator damage. A bad battery has damaged many perfectly good alternators.

And you don’t want your car’s alternator to become part of the statistics.

An alternator is meant to recharge the battery. This comes in handy, especially after the battery has been used to start the engine.

A huge demand is placed on the battery as it starts the engine, so it needs to be recharged immediately.  

Additionally, the battery needs to stay charged even as various components and electrical systems are used in the car.

The alternator’s prerogative determines how much to charge the battery. It does this by measuring the reference voltage and current from the battery.

And if it should find that the battery has a problem and the reference voltage is very low, the battery will be recharged by the alternator by default.

But you need to realize that the alternator has not been designed for recharging dead batteries. Essentially, an alternator strives to maintain the charge on a good battery.

So if an alternator starts to recharge a dead battery, it will begin to run hot, and it will ultimately get damaged.


A weak battery will cause a misfire.

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