Nobody likes the persistent presence of an unpleasant or particularly strong odor. When driving, smelling a strong smell like sulfur, or “rotten eggs”, is often an indicator of a serious problem.
The smell comes from the small amount of hydrogen sulfide, or sulfur, within the fuel. Hydrogen sulfide generally turns into odorless sulfur dioxide. However, when something breaks inside the vehicle’s exhaust or fuel system, it can inhibit this process and create the odor.
By-products and deposits that cause odor are remnants of incomplete combustion of burning gasoline and can be attributed to multiple system failures. If the odor only occurs briefly after using the engine at high revs, there is no serious problem to worry about. However, a persistent sulfur odor needs to be investigated. Listed below are 3 reasons why your car smells like sulfur.
1. Broken catalytic converter
The most likely culprit for a rotten egg smell, the catalytic converter is part of the vehicle’s emissions system. When gasoline reaches the catalytic converter, the converter transforms traces of hydrogen sulfide into odorless sulfur dioxide. It is designed to reduce harmful emissions by “converting” exhaust gases, such as hydrogen sulfide, into harmless gases. A broken or stuck catalytic converter cannot properly process sulfur gases and will make your car smell like rotten eggs.
If your catalytic converter is the cause of the odor, you need a new catalytic converter. If your converter is inspected and shows no signs of physical damage, another vehicle component has caused it to fail and needs repair.
2. Defective fuel pressure sensor or spent fuel filter
The fuel pressure sensor regulates the use of fuel in a vehicle. If a fuel pressure regulator fails, it ends up clogging the catalytic converter with too much oil. Too much oil prevents the converter from processing all of the exhaust by-products, which then leave the vehicle through the tailpipe and produce the rotten egg smell. An excessive amount of by-products can also build up inside the catalytic converter and cause it to overheat, also contributing to the odor.
In this case, the fuel pressure regulator problem can be fixed by replacing the fuel regulator or filter. A worn fuel filter leads to the same problems caused by a faulty fuel pressure sensor – an ingress of burnt sulfur deposits into the catalytic converter.
3. Old transmission fluid
If you have overlooked too many transmission flushes, the fluid can start to seep into other systems and unleash a rotten egg smell. Usually only occurs in manual cars, changing the transmission fluid as suggested by your car manufacturer can often solve the problem. Any leaks that have appeared will also need to be addressed.
Eliminate rotten egg smell
The best way to remove the rotten egg smell from your car is to replace the faulty part that is causing the smell. It can be a catalytic converter, fuel pressure regulator, fuel filter, or even old transmission fluid. Once the appropriate part is replaced, the odor should disappear.
It is important to pay attention to all the bad smells that surround your vehicle. In addition to sulfuric odors, smoky or burning odors can indicate serious problems such as an overheated engine, a fluid leak, or worn brake pads. Always seek the advice of an experienced mechanic when it comes to diagnosing and repairing vehicle components.