Rotten egg smell

[mckrishes]

Hello all. I have a 2007 Honda Odyssey EX. While driving down the road I noticed a very strong rotten egg smell. It was very bad and lasted for several minutes. Then it slowly went away. Shortly after I received a message on my display that said “check fuel cap.” In the past the check fuel cap has come on maybe 3 times. I would check the fuel cap and tighten it and be on my way with no other problems. No engine codes are showing on the display. Anybody have any idea what this could be. Where do I even begin figuring out what’s wrong here? Thanks.

Topic

[Charles]

The rotten egg smell comes from the reaction in the catalytic converter responding to the leak in the EGR caused by the fuel cap being loose. My wife did the same thing on her 2010 Odyssey. Just a little inattention when fueling the car can leave the fuel cap a little loose and cause the problem.

[mckrishes]

Thank you very much. I will ensure that the fuel cap is securely tightened and monitor the situation accordingly. Thanks again.

[hondaguy453]

Also, make sure your battery doesn’t look like it’s bulging from the sides. Overcharged battery also smells like that.

[Cameron]

[quote=”mckrishes” post=147108]Hello all. I have a 2007 Honda Odyssey EX. While driving down the road I noticed a very strong rotten egg smell. It was very bad and lasted for several minutes. Then it slowly went away. Shortly after I received a message on my display that said “check fuel cap.” In the past the check fuel cap has come on maybe 3 times. I would check the fuel cap and tighten it and be on my way with no other problems. No engine codes are showing on the display. Anybody have any idea what this could be. Where do I even begin figuring out what’s wrong here? Thanks.[/quote]

The rotten egg gas smell has absolutely nothing to do with the fuel cap being loose. They are totally unrelated.

The smell is not coming from the exhaust system or EGR system on the Honda but I believe you will find it originates from a bad battery. Battery fumes (hydrogen sulfide (H2S)) are seeping into the cabin . If you have caught the smell once it will happen again. Have the battery replaced as soon as possible and be extremely careful when removing the old one. Make sure you vent all the gas originating from the battery by leaving the bonnet open for a good time before removing the old battery. Batteries can blow if the explosive gasses inside the bad battery ignite. ( I have had this happen and it is no fun cleaning up the mess. Fortunately the bonnet on the vehicle was shut when it happened.).

The smell you noticed is from the battery overcharging and it is possible there might also be a problem with the vehicles charging system – Alternator and Voltage Regulator. Replace the battery and have the charging system checked by a professional.

[Ryan Marvin]

I am with cam in that I think the fuel cap being loose is unrelated. With that being said, I think it is either sulfer not being heated by the catalytic converter(bad cat) and burned off or potentially the battery. With no check engine light pointing to a p0420 though it is potentially not your catalytic converter. I think your cheapest route is to verify there are no cracks on the battery and connections are solid and if so have the battery load tested. Many places will do that for free. If the battery checks out, do a digital temperature reading of the catalytic converter and make sure its heating up on on the up a few hundred degrees more on the downstream side (side coming out of the tailpipe).

Best Regards,
Ryan

[Author]

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