Can Bad Gas Cause A Misfire – What Can You Do To Fix It?

Can Bad Gas Cause A Misfire – What Can You Do To Fix It?

Sometimes, while driving, you may have noticed some moments when the vehicle starts to stall or lose acceleration. A misfire causes this. But, can bad gas cause a misfire? A misfire occurs when one or more cylinders don’t produce the optimal energy required to drive the car’s wheels.

For movement to occur in a vehicle, you must send energy to the wheels via the engine. Combustion occurs in the cylinder chambers, where fuel and air are burned at high pressures to help produce enough energy that drive the wheels.

The factors that can cause an engine to misfire include bad spark plugs, gas octane rating, the ignition system, and electrical or mechanical problems. Amongst these causes of engine misfires, car owners usually ask a common and interesting question, can bad gas cause a misfire?

Yes! Bad gas can cause a misfire and not only that. Other complications now happen, and your car’s engine will experience frequent engine misfires when it goes unchecked. This article will fully discuss different complications that can cause your engine to misfire and what you can do to avert the situation.

We will also provide many more professional tips and advice that will help prevent engine misfires. Hence, stick with us as we answer the common question can bad gas cause a misfire?

Let’s dive right in.

Engine Misfire

As previously stated, engine misfires occur when one or more cylinders don’t produce the optimum power required to push the wheels into action. But it isn’t as simple as that. We will try to explain this complication in its simplest form. For the wheels to move, combustion has to take place.

Combustion happens in the cylinders and is a chemical reaction involving: oxygen (gotten from the air mixture), fuel, and the spark plug (to initiate the combustion process). These reactions occur in a split second to produce the energy that drives the wheels.

For this reaction to occur smoothly at such high speeds, it requires a step-by-step process coupled with the precisely timed addition of each of the ingredients mentioned above. That leads to a chain reaction.

A slight alteration in this process destabilizes the whole system, and the chain reaction is cut off, causing the engine to “cough, sputter, or stall .” Distinguished ladies and gentlemen, this is what we call an engine misfire.

An engine misfire may miss your observation because most of the time, the engine recovers in about 2 seconds after experiencing a misfire. It only becomes evident when there is a constant misfire and the vehicle begins to stall or decelerate.

Some drivers even notice the engine misfiring after filling the gas tank. And when this happens, they tend to ask, “Can bad gas cause a misfire?” That is completely understandable as they try to pinpoint what exactly might be the cause of an engine misfire.

So, what causes engine misfires? The next section will do justice to this common question.

Engine Misfire Causes

Among the various factors that can cause an engine to misfire, the most common include bad spark plugs, bad gas octane rating, bad ignition system (you can find out more in our guide on how long can I drive with a bad ignition coil), and electrical or mechanical problems. But amongst these common causes of engine misfires, car owners usually ask a common and interesting question, can bad gas cause a misfire?

Let’s tackle this question under the causes of an engine misfire.

Can Bad Gas Cause A Misfire

Bad gas in your gas tank can be likened to a ticking time bomb sitting in your car. Bad gas can cause further complications that can even knock your engine if adequate care is not taken. Before we explain the grave consequences of having bad gas, there are two types of bad gas in the gas market:

  1. Gas that is void of the required amount of dispersant-detergent additives.
  2. Gas that does not have the recommended octane rating.

Many drivers don’t understand various types of bad gases; hence, let’s go into detail about what they mean and how they can cause an engine to misfire.

Can Bad Gas Cause A Misfire #1. Gas Void Of Sufficient Dispersant-Detergent Additives

Before gas is distributed to consumers, certain additives known as dispersant-detergents are added to the gas to prevent gas residues from clogging fuel injectors. Sometimes gas suppliers try to cut corners with this procedure to save a few pennies per liter.

They may reduce the quantity of dispersant (detergent) added to the gas or may use a less effective, cheaper product that will cause further complications. Even when these additives are added, “fluidizers” are also recommended to be used to prevent gas thickening caused by these additives.

When gas suppliers do not follow due process before distributing the gas, fuel injection systems are affected (if you want to learn more, check out our overview of what do fuel injectors do). A clogged or bad fuel injection system caused by a bad gas will cause an engine misfire or multiple engine misfires, depending on the gravity of the damage.

That is because dirt in fuel injectors will affect the rate at which fuel is injected into the combustion chambers. Once inadequate fuel is made available at the right time, a lack of insufficient fuel will lead to insufficient combustion; hence an engine misfire results.

One of the best gas additives that don’t even require a “fluidizer” is Polyether amine. However, gas suppliers don’t use it because it costs double the price of other additives. Notably, 85% of distributed gas doesn’t contain the appropriate amount of additives and hence can be called “bad gas.”


Can Bad Gas Cause A Misfire #2. Gas With Bad Octane Rating

According to Wikipedia, an octane rating is a standard measurement of a fuel’s ability to withstand compression in a combustion engine without detonating. Each vehicle has its own gas octane rating recommendation.

Using gas with a lower octane rating than recommended usually leads to an engine knock. An engine knock is a nightmare for all drivers. Using fuel with the recommended octane rating prevents fuel that hasn’t been ignited from bursting into flames.

In conventional combustion engines, the air is drawn in by pistons and compressed to high pressures. Once at high pressure, fuel is immediately injected via the fuel injectors and ignited by the spark plugs.

An exothermic combustion reaction rapidly generates energy that drives the wheels. This process repeats itself many times per second. This rapid cycle is often measured in revolutions per minute (rpm).

Bad octane gas causes problems because, with a lower octane rating (i.e., easier to detonate when compressed) than recommended, the fuel still yet to be injected for combustion can detonate during the first compression cycle.

This detonated gas can cause vibrations and shockwaves, which can “knock the engine.” There are three grades of gas with different octane ratings for separate vehicles.

  1. Regular gas (octane number 87): Most regular cars use gas with this octane rating.
  2. Mid-range blend (octane number 89): used by some performance cars
  3. Premium gas (octane number 91): used by heavy-duty trucks and muscle cars.

The price of each varies by a few cents, with premium gas being the most expensive and regular gas the cheapest.

Can Bad Gas Cause A Misfire #3. Contaminated Fuel

Fuel contamination is a significant concern for vehicle owners. Water, dirt, or other foreign substances in the gas tank can interfere with proper combustion. When water mixes with gasoline, it prevents the fuel from burning efficiently, leading to engine misfires.

Always refuel at reputable gas stations. Sometimes, underground storage tanks can corrode, allowing water and rust to mix with gasoline. Also, avoid refueling your car during a gas station’s tank refill as this can stir up debris settled at the bottom.

Can Bad Gas Cause A Misfire #4. Old or Stale Gasoline

Gasoline isn’t timeless. Over time, it can degrade and lose essential volatile compounds, especially if the car remains idle for prolonged periods. Stale fuel doesn’t combust as efficiently as fresh gasoline. This inefficiency can cause sputtering, rough idles, and yes, misfires.

If you suspect your gas is old, try adding a fuel stabilizer. For vehicles in long-term storage, it’s recommended to drain the fuel system or use stabilizers to maintain fuel quality.

Can Bad Gas Cause A Misfire #5. Clogged Fuel Filter

Your fuel filter plays a pivotal role in keeping impurities from entering the engine. Over time, however, this filter can become clogged with debris. A clogged filter restricts the flow of gasoline, causing an uneven supply to the engine. This can, in turn, result in misfires.

Regular maintenance and timely replacement of the fuel filter can prevent this issue. If you notice a decline in your car’s performance, consider checking the fuel filter.

Can Bad Gas Cause A Misfire #6. Faulty Fuel Pressure Regulator

The fuel pressure regulator ensures your engine receives the right amount of fuel. If this component fails or becomes faulty, it can send an incorrect amount of fuel to the combustion chamber. Too much fuel (flooding) or too little can both cause misfires.

Inspecting the fuel pressure regulator and maintaining the fuel system can help address this potential cause of misfire.

Can Bad Gas Cause A Misfire #7. Fuel System Air Leaks

Air leaks in the fuel system can disrupt the ideal air-to-fuel ratio required for combustion. Vacuum leaks or leaks in the intake manifold gasket can introduce additional air into the system, leading to lean conditions. A lean condition means there’s more air than needed, resulting in incomplete combustion and misfires.

Regular inspections can help identify and fix potential air leaks, ensuring smooth performance.

Can Bad Gas Cause A Misfire #8. Fuel Pump Issues

The fuel pump is responsible for transporting gasoline from the tank to the engine. A weak or malfunctioning fuel pump may not deliver fuel consistently, causing an intermittent supply. Intermittent or reduced fuel supply can result in misfires.

Listen for any unusual sounds from the fuel pump and monitor your car’s performance. If you suspect an issue with the fuel pump, it’s wise to consult with an automotive expert.

Can Bad Gas Cause A Misfire #9. Ethanol Concentration Variations

Today, many gasoline options contain ethanol, a biofuel. While vehicles can handle a specific ethanol concentration, like E10 (10% ethanol), higher concentrations might not be suitable for all cars. Gasoline with higher ethanol content, such as E15 or E85, can cause combustion issues in vehicles not designed for such fuels, leading to misfires.

Always ensure you’re using the recommended fuel type for your vehicle.

Can Bad Gas Cause A Misfire #10. Fuel Injector Malfunctions

Apart from clogging due to bad gasoline, fuel injectors can also malfunction due to electrical issues or wear and tear. A malfunctioning injector can either flood the combustion chamber or fail to deliver enough fuel, both of which can cause misfires.

Routine checks and cleaning can ensure the longevity and efficiency of your fuel injectors.

In conclusion, while bad gasoline can undoubtedly lead to misfires, many factors within the fuel system can cause similar issues. Regular maintenance and vigilance can help prevent these problems and ensure a smooth drive. Always consult with automotive professionals if you encounter persistent or severe engine problems.

How To Know The Best Octane Rating For Your Engine

Most of the time, fuel pumps come with tags with the numbers 87, 89, and 91. That represents the gas octane number found in these gas pumps. Simply check your owner’s manual to find the best octane rating for your car. Or check the internet at their official sites.

Gas with a low octane rating can damage your engine by knocking it! A bad engine can cost about $2500 – $3500 in repairs. It’s better to lose a few cents at the gas pump than lose $3,500!

Sometimes gas suppliers can cut corners and defraud you by selling mid-range or regular gas for the price of premium gas. Keep an eye out for a drastic reduction in fuel economy compared to normal. This might indicate fraud from the supplier if you bought the premium range of gas. It is recommended you report to local authorities for a gas station inspection.

Next time you feel like asking the question, “Can bad gas cause a misfire?Also, ask yourself the question, “Am I using the best octane gas rating?”. If your answer is “NO,” you might want to consider making a U-Turn to avoid further complications.

Faulty Spark Plugs Or Ignition System


As we already know, spark plugs play a crucial role in combustion engines. As the name implies, it initiates combustion by introducing a spark to the air-fuel compressed mixture. A faulty spark plug means that the ignition is messed up (which you can confirm by figuring out how to test a spark plug).

The mixture is ignited at the wrong time (if ignited at all) and causes the cylinder to lose power, or an engine misfire occurs. Corrosion in spark plug wires can be the culprit and should be checked. Spark plugs also have a short lifespan and require a routine checkup and renewal.

Another problem that can cause a misfire is an air gap. When spark plugs are not properly fitted, a little air gap forms, and a compressed fuel-air mixture leaks from this gap. A leakage will alter the combined ratio, and hence a misfire will occur.

Ignition coils convert low voltage from the battery into high voltage needed by the spark plugs to ignite. When these ignition coils wear out or go bad, they will generate insufficient voltage, and the spark plug will not ignite. That makes a cylinder lose power or misfire.

While troubleshooting for possible causes of a misfire, invite a technician to check all relevant components to avoid more damage to the car engine.

Mechanical Problems

An engine compartment is basically a house filled with moving parts and components. These movements cause friction, and many components can go bad with friction. Vacuum leaks can be caused by cracks that prevent appropriate compression of air and fuel; the result is an engine misfire.

The problem could come from broken or leaking valves, belts, chains, springs, gaskets, seals, etc. Do a thorough check on all engine components to detect if the misfire is from a mechanical problem. That is because, as previously mentioned, an engine misfire can be caused by any random factor, and if it is not tackled on time, an engine might get damaged.

Engine Misfire Symptoms


There are common symptoms associated with engine misfires. So what does an engine misfire feel like? You must know these symptoms if you don’t. Knowing engine misfire symptoms can save you a lot of money in detecting and solving the problem on time before it gets out of hand.

Here are the symptoms of an engine misfire.

Can Bad Gas Cause A Misfire, Symptoms #1: Slow Acceleration

Have you ever experienced pushing the accelerator pedal hard and your car accelerating slowly? An engine misfire may have caused that experience. Since a cylinder loses power, it makes sense to say that acceleration is immensely affected.

Slow acceleration occurs when the engine operates at full load and the driver keeps stepping on the accelerator pedal. You may want to contact your mechanic once you experience slow acceleration in your vehicle.

Can Bad Gas Cause A Misfire, Symptoms #2: Noisy Engine

It is already a general observation that a “coughing, sputtering or spiky” sound (for more insight, check out our explainer on sputtering engine when accelerating) indicates when an engine misfires. An interruption in the combustion chambers causes the pistons to make this noise. A mechanic should check for any observed noise from the engine compartment as soon as possible to avoid throwing more money on the table.

Can Bad Gas Cause A Misfire, Symptoms #3: Thick Exhaust Smoke

Whenever you notice dense black exhaust smoke from the exhaust pipes, you want to check your engine compartment. Black smoke indicates that there is a problem with combustion in your cylinders.

Black carbon soot might mean that the fuel-air mixture ratio is compromised. Lack of adequate oxygen will cause the combustion to be incomplete, resulting in thick black carbon smoke.

An engine misfire is suspected, and if a misfire is not the problem, you should get a mechanic to help troubleshoot your engine compartment.

Can Bad Gas Cause A Misfire, Symptoms #4: Check Engine Light Turns On

Due to the presence of chips and sensors in a car engine, they can detect a faulty engine component and alert the driver with the “check engine” light on their dashboard. Always check your dashboard immediately after turning on the ignition for these error signals or codes. You can learn more in our guide on check engine light after oil change.

Cylinder Misfire Fix


Cylinder misfires can greatly damage your car’s engine if it goes unchecked for a long time. How can you fix a random cylinder misfire? It is important to note that the error code for random cylinder misfires is P0300. Once this code is detected, it shows that one or more of your cylinders have misfired.

Many issues can cause this code to come up, including faulty spark plugs, zero-cylinder compression, clogged valves, vacuum leaks, faulty engine sensors, and a host of others.

Here are some tips on fixing a random misfire using basic DIY tools.

1. Identify The Misfiring Cylinder

If you have gotten to this point in the article, you must know how to detect if your engine is misfiring. The next step is to pinpoint the exact misfiring cylinder.

You can do this by using a scan tool which you can get from local stores. Using the scan tool to scan your vehicle will produce a code, for example, P030(1). That shows you that the misfire is detected in cylinder number 1.

Using your tools, get to work removing the plastic topper on your engine. In case you are confused about locating your cylinder 1, use a Google image search, and you will find many useful resources at your disposal.

Here is a YouTube video on how to use an engine scan tool.

2. Swap The Coil Packs

Coil packs are found mostly at the top of the engine, just above or below the spark plugs. You can try swapping the coil pack from cylinder 2 to cylinder 1. And if the engine stops misfiring after the swap, then the coil pack of cylinder 1 needs to be changed. Again, you can consult YouTube for a detailed explanation of how to remove and swap your engine coil pack because different cars have different engine settings.

3. Check Your Spark Plugs For Signs Of Damage

If the problem is not solved after swapping the coil packs, remove your spark plug and check for any signs of rust using a spark plug remover. If any debris is found on the spark plug, you can clean it using a sample of paper or fuel and allow it to dry before inserting it back. Make sure to tighten the spark plug as recommended to avoid creating an air gap.

You can also try swapping the spark plugs from different cylinders to pinpoint if it’s a spark plug issue. Once it is certain that your spark plug isn’t the issue, move on to the next step.

4. Use A Multi Meter To Check The Coil Pack Connectors

The problem might be caused by voltage not reaching the coil packs from your battery. This problem can be detected by using a multimeter. Set your multimeter to DC mode. The black wire is the earth and should be connected to a metal component on your engine, while you connect the red wire to a metal point in the coil pack wire.

The standard car battery voltage will get a reading of about 12 volts. Anything less than that could be from a weak battery or damaged wires in the coil pack.

A YouTube video showing how to test coils

5. Check The Fuel Injectors

All cylinders have dedicated fuel injectors, and fuel injectors can be the cause of engine misfires. Using a multimeter, you can run a resistance test on the fuel injector of the affected cylinder.

Recalibrate the multimeter to show the Ω symbol and connect the multimeter to both fuel injector prongs to perform a resistance test. A reading should be seen, and a good injector should have a reading of around 9 to 14 Ω (ohms).

Any reading that varies widely from the average reading shows a bad fuel injector and can cause an engine to misfire.

6. Visiting A Mechanic

Chances are that once you get to this stage, you might have successfully identified the problem causing the misfire. However, other complications can result in engine misfiring, and we recommend you visit the mechanic.

Trying out our recommended DIY techniques should be done with absolute caution to avoid damaging engine components. If you get confused at any stage, you should stop further actions and call for the services of a mechanic.

Can Bad Gas Cause A Misfire: In Conclusion…

Asking the question, can bad gas cause a misfire? shows that you may have experienced certain difficulties with your car’s engine after filling up the gas tank (and making sure you don’t accidentally put diesel in your gas car). And the simple answer to that question is that bad gas can cause misfires. We have two types of bad gas, namely:

  1. Gas with a low octane rating
  2. Gas void of detergent- dispersant additives.

Any of the above-listed types of bad gas can cause an engine to misfire. You can learn more in our guide on whether can you put diesel in a gas can. Apart from this common cause of engine misfires, other factors include bad spark plugs, bad ignition systems, and electrical or mechanical problems.

Symptoms of a misfire include black exhaust smoke, a noisy engine, and slow acceleration. There are also tips on fixing a random cylinder misfire, including checking for bad spark plugs, worn-out timing belts, or bad ignition coils (which you can confirm by learning how to test a coil). We have laid down some basic DIY techniques you can use in troubleshooting your car’s engine if you notice symptoms of a cylinder misfire.

However, it is advised that you seek the services of a qualified mechanic if you get confused while applying our DIY techniques. We sincerely believe we did justice to the question: Can bad gas cause a misfire? We frequently update this blog with several other articles that cover different car-related issues and what to do about them. See you at the next one!

Can Bad Gas Cause A Misfire: Frequently Asked Questions (FAQs)

Here are some frequently asked questions about whether or not can bad gas cause a misfire…

How To Fix Engine Misfire

Fixing an engine misfire can range from replacing a worn-out spark plug to changing the bad gas in your tank. Many other complications can occur, which cause an engine to misfire. If you cannot detect the problem, consult a mechanic.

What Is A Misfire

A misfire happens when one or more cylinders in your car engine lose power, causing the vehicle to stall or decelerate. When misfires occur, one or more components necessary for combustion in the cylinder are bad or have inaccurate timing.

What Does A Misfire Sound Like

Coughing, sputtering, or cranking noises are heard from the engine compartment whenever a misfire occurs.

What Does A Misfire Feel Like

A moving car will stall or lose acceleration when a misfire occurs. You get lesser acceleration when you step on the accelerator pedals.

Can A Bad Battery Cause A Misfire

Yes. A bad battery can cause a misfire by causing a weak or no spark at all in the spark plugs.

What Causes A Misfire

A bad battery, gas, spark plugs, weak or damaged ignition coils, etc., can all cause a misfire.

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