Can a Bad Battery Cause a Misfire?

Among a ton of issues related to a car, an engine misfire is the most annoying one for sure. You start the car well and have all the electronics running as obvious, but the misfire is an uncertain one. Although there are other reasons for a misfire, the question remains is:

Can a bad battery cause a misfire?

Well, not really. A bad car battery alone cannot possibly cause a misfire in a spark plug within the combustion engine. The spark plugs are powered solely by the alternator and the Engine Control Module (ECM). However, if the battery is leaking electrolytes or the charging system is faulty, you can have a misfire.

The process goes a little complex. Let’s walk you through the possibilities and how to avoid a misfire in the engine.

Misfires: What and How

The car runs on a combustion engine that has a spark plug to fire the compressed air and fuel mixture. So, if one or more spark plug has gone wrong at any point, it will misfire, and potentially the engine might not run at all.

Here are the types of misfires you might experience:

Spark Plug Misfires

Spark misfire is the misfire everybody mostly faces and means by a misfire or a Mi Error code. It’s a small part of your car’s combustion engine that ignites the compressed fuel and air mixture and starts the combustion reaction to move forward.

Fuel Misfires

The fuel pump is a part of the process that an engine goes through right before the compression happens and the spark plug ignites. If you have an issue with the pump or the filter, like it’s clogged, it will misfire. If this happens, cleaning the pump and relevant ways or changing dirty fuel is enough.

Mechanical Misfires

This is by far the most damaging type of misfire. It can be complex to diagnose and fix because it can an issue with anything in the mechanical drive system. The problem can be with the drivetrain that, when gone wrong, can damage the entire combustion process.

Luckily, mechanical misfire is a very uncommon issue you might face while handling a car engine. If this happens, it’s time to see a professional certified car mechanic.

In the cases of spark plug or fuel misfire, the fixing can be easy and not so expensive of a process.

Can A Bad Battery Cause A Misfire?

Since the spark plug is the one that you will face 98% of the time, let’s talk about only that. Let’s see if a bad battery can be among the causes that can cause a spark plug to go wrong.

The straight answer is the battery will not directly have any connection with the misfire for the spark plug of your car engine. As mentioned earlier, the spark plug runs on the alternator. And the alternator is also connected to and recharges the battery.

Even though it’s connected to the battery, it doesn’t draw power from the battery, but it recharges it. Therefore, you don’t have a power circuit from the battery to the spark plugs.

However, there are a few situations when a bad battery can indirectly cause a misfire as well. Some of those situations would be:

Corrosion and Overcharge

Corrosion and other debris can be bad for the spark plugs and the associated parts. If you have a heavily corroded battery, and it’s placed very near the engine cylinders, the corrosion can make its way into the spark plug connectors. That’s when the battery can indirectly hamper the function of the spark plugs.

Voltage Irregularity

If the electrical circuitry of your car senses overly irregular voltage fluctuations, it can hamper the functionality of the alternator. If the battery is causing the irregularity, this possibly can make its way into the spark plug through the alternator. You might have to regulate the battery or the ECU in this case.

Excessive load

A bad battery can possibly put a lot of load on the alternator. That, as a byproduct, can strain the output of the alternator to other electronics. And that includes the spark plug, the fuel injector, and everything that draws electricity from the alternator to ignite the fuel injection.

The injector might not open up fully, or the coil might not fire enough to ignite the combustion in this case. You want to check this up with a multimeter whether the alternator is providing more than 12V of power to each place it should.

Dripping Battery Fluid

If you have the alternator wires running under the bad battery, that can have a lot to do with the misfire. You want to make sure the battery is not that bad, so it spills out fluid or tosses around corroded crystalline deposits.

Make sure you have a clean connection to and from the alternator. Only that way, you can have a properly functioning alternator that does its job keeping the spark plugs working.

Possible Causes of A Spark Misfire

So, what’s causing a misfire in the spark plug? Here are the reasons why you may have a spark plug malfunction or even a misfiring one:

Faulty Spark Plugs

The most common reason for having misfires is having bad spark plugs in the first place. If you have a bad spark plug, it will not be able to ignite the fuel as it should. Plus, it can have a higher gap between the spark plate and the igniter.

Don’t go beyond or less than the gap recommended by the manufacturer. Ideally, you need to change the spark plugs every 20,000 to 30,000 miles. Or there’s a good chance for it to burn out.

A Bad Alternator

For the most part, the reason for misfires will be a bad alternator, which is somewhat related to the battery in your car.

If you have a bad alternator or if it has a bad connection to the ignition coil, you’ll have random misfires.

The best way to get this fixed is by inspecting which part of the system is affected. If the connections are bad, corrode, or worn out, replacing or fixing them will cover it.

A Faulty Ignition Coil

The ignition coil sends the signal for a spark. When it’s faulty or covered in dirty engine oil, it can’t function as efficiently as it should.

If you’re experiencing a spark misfire, do check the coil for defects.

If it’s covered in engine oil, clean the coil using a suction tool and a screwdriver wrapped with tissue or microfiber cloth.

Bad Coil packs

Apart from the ignition coil, you can also have the coil packs faulty. These are the connection points for the spark plugs that supply current to the plugs to ignite.

When inspecting, be sure the check if every pack is nice and tight to the openings, and they don’t come off too easy.

If they’re showing signs of wearing out, be sure to replace them to get the misfire issue fixed.

Flat Valve Cover Gasket

The spark port holes have rubber cover gaskets in them to prevent air or fluid leakage and penetration.

If the gaskets are flat and not doing what they should do, you will have random misfires. In such a case, all you have to do is, change the set of flat valve cover gaskets and replace them with a new set.

Water in the Fuel line

The fuel line is the sole provider for the spark plug to have fuel in it to ignite. If you have water or bubbles in the fuel line, this will cause random misfires as well.

Check the fuel line and be sure it’s in good shape by inspecting the inside. If it’s clogged or leaking, replace the fuel line, and you will have a functioning spark system.

A Bad PCB Valve

A crankcase breather valve can give you random misfires because of the vacuum leak and show code for misfires. It can be super hard to diagnose this one as it’s not a usual issue to face. If it’s the reason, you just have to replace the valve.

How To Identify & Resolve A Misfire?

When you have a misfire issue in your car’s engine, you can identify that in a few ways.

• You’ll hear a strange noise and frequent power drop
• The dashboard will show a misfire error code
• If you can smell the unburned fuel from the spark plug while driving
• Check engine light error on the Dashboard
• Heavy vibration in low RPM (misfire goes away at high RPM sometimes)

If you have a faulty spark plug, here’s a guide that will help you replace that on your own:

Final words

A bad battery is not the thing you want to deal with when it comes to a malfunctioning car or car engine. It can cause a ton of problems from starting the engine in the first place, to the smaller ones like running the stereo.

Although experiencing a misfire is not usually a result of a bad battery, it can definitely make its way into that. Now that you know everything about the misfire you’re experiencing, you should now be able to diagnose the issue and resolve it like a pro.