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Can an Exhaust Leak Cause a Misfire? (Explained)

As a vehicle ages and crosses a certain mileage, different issues start to surface. Exhaust leaks are a common issue. The leaks may cause different harmful mishaps.

You can find the issues and the steps to fix exhaust leaks, and other relevant questions below.

Can an exhaust leak cause a misfire?

Misfires directly due to exhaust leaks aren’t very common but are a probable cause. The most common causes of misfires and backfires are due to misadjustment of the ignition timing or valve timing. Wrong reports to the PCM from the leak, however, can cause a misfire.

Misfires due to exhaust leaks are improbable but not impossible. Exhaust leaks usually produce a staggering broken exhaust noise which is often misdiagnosed by drivers as misfiring.

When your vehicle has an exhaust leak, there could be an imbalance of the air-to-fuel ratio in the cylinder.

This imbalance can bog down the fuel efficiency as well as emit harmful fumes such as carbon monoxide.

Besides that, the leak will cause your engine to work inefficiently harder, as a result, depleting your fuel faster. Thus, if you smell smoky gas fumes, then it is a sign of an exhaust leak.

Not only is the smoke harmful to your health but it can have detrimental impacts on your vehicle and needs immediate attention before it gets worse.

The smoky fumes cause the spark plugs to get covered with a layer of soot and get fouled. Thus the fouled plugs cause a misfire.

How does an exhaust leak cause a misfire?

If an exhaust leak is causing huge amounts of leaks, then it can mislead the PCM to increase fuel delivery according to the reported false lean condition.

Therefore, the bank of cylinders will have surplus fuel, resulting in spark plug carbon fouling and misfires.

Exhaust gases travel as pulses of high and low-pressure zones. Exhaust gases leak to the outside at high pressure, while outside air gets sucked in at low pressure. As a result, the upward oxygen sensor misreads and misreports the fuel amount.

The PCM gets a false lean condition report from the oxygen sensor and increases fuel delivery. Since there is exceedingly high fuel now, the spark plug gets fouled with carbon deposits and causes misfires.

What can I use to fix an exhaust leak?

What items you can use to fix the exhaust leak depends on the location and size of the leak. Below, you can find a list of items commonly used to fix an exhaust leak:

Replaceable gaskets:

If the leak occurred due to blown gaskets, it can be easily fixed by replacing the bad gasket with a new one.

Weld the leak shut:

Welding the leak shut is a much durable and long-lasting solution and should be done if the exhaust isn’t rusted.

Seal with epoxy bonds and exhaust tapes:

Exhaust tapes can be used to seal small leaks while larger leaks require an additional patch on top of the epoxy bond.

What are the symptoms of an exhaust leak? What problems it can cause?

Exhaust leaks have several visible, audible, and physical symptoms. If you suspect an exhaust leak, you should check out the following symptoms:

Unusually Loud Exhaust:

A hole in the exhaust will produce an unusually louder noise, especially when driving. So, if you notice loud noises coming from the exhaust while you are driving, then it is possibly a leak.

Staggering Noises:

Depending on the size of the leak, you will hear all sorts of noises and sounds. Narrower leaks tend to make higher-pitched noises while wider leaks will make low-pitched noises. 

The sounds are more apparent from the outside of the vehicle and get louder as you rev the engine.


Air leaks through a crack, broken gasket, or holes cause unwanted metal vibrations. Although it is not apparent from within the vehicle, it can be noticed upon closer inspection from the exterior.

Lower Gas Mileage:

If you end up refueling your vehicle more frequently, then there could be a possible leak. Exhaust leaks fool the sensor causing the Engine Control Unit to prompt the vehicle to use more fuel.

Smelling Exhaust Fumes:

The exhaust’s primary function is to prevent you from breathing in the exhaust fumes. If you can smell the fumes, then the exhaust has leakage.

Carbon Deposits on the leak:

Carbon soot deposits around the leakage area of the exhaust. So, if you notice black spots in your exhaust, it could very well be the source of the exhaust leak.

Holes in the exhaust system:

If you see visible holes in the exhaust, that is definitely the cause of the exhaust leak and needs to be sealed up immediately.

Can an exhaust leak cause loss of power?

Contrary to the popular belief, the loss of power due to the holes in the pipe will not be significantly noticeable.

However, leaks caused by dents or crushed exhaust will severely restrict gas flow and cause a loss of power. Comparatively, drivers will experience drastic changes in gas mileage while slight loss of power.

Interestingly in some cases, drivers experienced a gain in power when the exhaust got crushed. If the tubes are crushed flat, there will be a loss in power, but if it is partially crushed then there might be an increase in power and torque.

How to fix an exhaust leak?

Exhaust leaks needed to be immediately repaired since they are harmful to health. That being said, it is not advisable to repair the leak yourself and seek professional help. 

In case you need to fix the leak yourself, you can get some Epoxy Bonds, Exhaust Tapes, and Patches and follow the steps below:

Locate the exhaust leak:

To locate the leak, park your vehicle on solid and level ground and allow your exhausts to cool, if warm. 

Afterward, jack your vehicle up as required and investigate the exhaust for visible signs of damage. In case you cannot find the leak, you can start the vehicle and look for smoke leaks.

Cleaning the leaked area:

Once you locate the leak(s), use a brush with firm nylon bristles to rub off and remove the debris from the surface of the pipe. 

Make sure you’re wearing eye protection and a mask to prevent the dirt from getting into your eyes or causing an allergic reaction.

After the initial clean-up, use a piece of grit sandpaper and scrub the leakage area. If the leak size is small, make sure to scrub all around the pipe. 

For a finishing touch, you may choose to wipe the area with a bit of acetone as well; if you don’t have acetone nearby, nail polish removers will work as well.

Sealing the leak:

Smaller leaks can be dealt with just using epoxy or exhaust tapes. If you are using exhaust repair tape, wrap at least two layers all the way around the pipe. Also, wrap a few inches on both sides of the leak to prevent side leaks.

Larger leaks have to be dealt with epoxy bonds along with patches. To do so, you need either a patch kit or a used canned food can for the patching and a mixture of the epoxy bond. 

Apply the mixture of the epoxy bond on top of the leak and place a small cutting from the can on the paste.

Dab the epoxy mixture on the can cutting and cover it with a cylindrical can cutting. Once you have placed the patch, firmly lock the patch with hose clamps and leave it to dry for a minimum of 6 hours.

Is an exhaust leak easy to fix?

Exhaust leaks are easily fixable due to their location and simplicity. If your exhaust is rigid, you can fix it yourself with the steps above. However, rusted and fragile exhausts should be replaced with a new ones instead.

You can also take your vehicle to an auto repair shop as well. Although it would cost more, servicing at an auto-repair shop would provide a longer-lasting exhaust.

How much does it cost to fix an exhaust leak?

The cost of fixing an exhaust leak is flexible and budget-friendly. Although the cost depends on the size and number of leaks, you can choose to opt for a costly durable fix or a cheap stable fix.

If you choose to have it fixed at a repair shop, expect to pay $160-$330 for labor costs and parts costs.

And if you are fixing it yourself, the parts required will cost between $15 and $50. Fixing at a repair shop is advised if your exhaust is in a very poor condition.

Final Thoughts:

In conclusion, misfires are rarely caused by exhaust leaks but they can cause other problems that eventually lead to a misfire. Leaks in the exhaust would misinform the oxygen sensor and prompt the PCM to inject fuel. These events foul the spark plug and result in a misfire.