Why Does My Car Smell Like Gas When The AC Is On?

Is your car smelling like gas when the AC is on? If that's the case, you need to fix it right away! Here are all the possible causes and potential fixes.

Noticing a gas smell may indicate a very serious underlying problem, but also something insignificant like a loose gas cap. This article will go through the most common causes and the most expensive ones.

Gas – some might argue it has the best and most addicting smell in the world.

While inhaling gas might be satisfying for some, it is not a good sign to notice a gas smell while you are driving your car.

First, it is important to take into consideration that not all cars are built the same. Older cars do not use fuel injection but carburetors instead. The focus will be modern cars built from 1990 and beyond.

Let’s get started with the most common causes!

Related:Why Is My Car AC Blowing Hot Air? How To Fix

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The Most Common Cause

man and bad smell inside car

So, why does your car smell like gas when the air conditioner is on? The most common cause is mold and bacteria.

While mold and bacteria may not smell exactly like gas, many people may mistake the odor of mold and bacteria for gas. Luckily, this is an easy fix – a change of your AC filters and an antiseptic treatment usually do the trick.

This tends to happen if you have not used your air condition for a while. It is therefore important to regularly change the filter and properly maintain your car.

Is It Something Else?

If mold and bacteria are out of the question, a gas or fluid leak is usually the culprit. If this is the case, you should take your car to your trusted mechanic as soon as possible.

Do not panic just yet. It is wise to look for less serious and simple causes first.

The Gas Cap!

Car gas cap

A very easy fix and a relatively common problem might be due to your gas cap. It may be improperly closed after you fueled up your car, or maybe there is a crack in it, letting out the fumes and the smell.

If it turns out that it is not properly shut, simply make sure you close it properly and the problem is solved! A cracked gas cap is not very serious and can be solved by simply buying a new one. The best bet is to go with OEM.

Loose Spark Plug

two spark plugs

Just like a relationship without a special spark is nothing to keep, neither is an engine without its spark plug(s).

The spark plugs are responsible for igniting the fuel/air mixture creating a small fireball, enabling a great amount of energy needed to make your wheels spin. One or more spark plug might be cracked or loose, leading the gas fumes to escape to the driver or passengers.

Replacing the spark plug is very easy and takes a few seconds to do. If you are doing it yourself, remember to work in a safe environment. AutoZone has a great guide if you want to do it yourself.

Leaks in the System

After looking through the elementary causes with no success, a leak of some sort should be the main concern. Below are different types of leaks that possibly are causing you a headache.

Speaking about headaches – gasoline contains carbon monoxide. An odorless gas that makes your blood (hemoglobin) unable to bind oxygen.

It is therefore of most importance to turn off and leave your car immediately. If you experience any severe headache, tiredness, or nausea, be sure to seek medical attention.

Also, keep in mind that fuel is highly flammable. If you suspect a fuel leak, do not under any circumstances smoke in, or around your car as it is a big fire hazard.

Fuel Tank Leak

pumping gas into car at gas station

 Maybe, your right foot is not so heavy after all. The reason for your fuel indicator dropping faster than usual might be a leak in the fuel tank!

The fuel tank stores all the gas in your car, unless it leaks of course, then your fuel will drip away. The smell is very strong, and you might see rainbow-colored fluid – that is your precious fuel freeing itself.

The fuel tank may be leaking without seeing visible gas beneath your car. If it turns out that a leak is the cause and no fluid is seen, chances are that it can be fixed without changing the whole tank.

Antifreeze Leak

green antifreeze

Imagine driving around a hot summer day with your AC on and enjoying the sweet smell of flowers and trees blossoming. Except that it is not the flowers that smell, it is your antifreeze.

If you smell gas while your AC is on, chances are that your air conditioning system is blowing the sweet smell of antifreeze in your cabin.

Your antifreeze does not only prevent your car from freezing, it also prevents your car from overheating. Therefore, you should promptly look up the problem to prevent more serious damage.

Fuel Line Leak

Not only can the fuel tank leak, but also the fuel line which delivers the fuel to your engine. This is more uncommon than other potential causes listed in this article.

Just like any other type of fuel leak, you should leave this job to your mechanic that probably will replace the faulty lines.

Leaking Fuel Injectors

Remember how the spark plugs created the small fireballs in the engine? Without fuel injectors, it would not be possible; they are responsible for… well… injecting fuel.

The fuel injectors distribute gas to the cylinders of the engine. If a leak is present, it leads to a gas smell in the close environment of the car, including the cabin.

If you detect a strong gasoline smell from your exhaust, there is a big possibility that your fuel injectors leak. However, in this case, they do not leak outside of the engine, but inside.

An internal leak of the fuel injectors means that fuel is overflowing the cylinders, making the engine unable to burn in and therefore leaves the exhaust unignited.

Other Causes

The most serious and common causes have been listed. If it turns out neither of those is the cause of the problem, it might come to something more delicate.

Modern cars are turning more and more technological in the sense of using lots of sensors, computers, and the like. Almost all functions and reactions are controlled by the ECU.

Chances are that a defect mass airflow sensor (MAF), O2 sensor, fuel pressure sensor, or alike makes your car combust more or less fuel than it should, leading to a distinct smell in the cabin.


The reason why your car smell like gas when the AC is on may be due to many different reasons. Some easy fixes include a contaminated air conditioning system, a loose gas cap, or a cracked spark plug.

Other reasons can be a bit more complicated to access but do not necessarily mean they are an expensive fix.

Remember that a fuel leak is a potential fire hazard and should be treated with extreme caution. If you feel nauseous, have a headache, or experience other abnormal symptoms, you should seek medical help and leave your car as soon as possible.

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Bajro Muric
Bajro Muric

Bajro is a big car enthusiast with a love for writing and teaching. He writes about anything regarding cars - from common problems and fixes to racing.