Long, but hopefully worth the read...
This is not a "what is that smell post?". If you've had a GS (or any Toyota/Lexus) you have most likely smelled the sulfur / rotten egg smell under hard acceleration. Typically the smell is more prominent when you have windows/sunroof open. If you haven't experienced this, you can stop reading now. For those who know the smell, it's been well documented that the smell is a by-product of the catalytic converter which is rumored to be related to use of certain gasoline(s) or possible issues with the catalytic converter itself. I have never really cared what is causing the smell, but have been very concerned with the idea exhaust is continuously coming in the car. The sulfur smell is something that you get under hard acceleration which makes you aware of the exhaust. The reality is most exhaust fumes have no smell so it's still coming in your car much more often than you think. Multiply this by 2 kids riding in the back seat and you end up with me on a crusade to stop it so I can keep the car I like.
Political Approach-
I specifically took the car to my Lexus dealer to have someone ride with me to experience the smell. They acknowledged smelling the rotten egg / sulfur smell in other cars. I took the service manager for a ride, went on the interstate, floored it an we took a bath in the smell for a good 15 minutes because I wouldn't stop making it happen (wanted to prove a point). He said he smelled it and would have someone take a look to see if anything was "wrong" with the car. In the end they reported there was nothing they saw that was not up to spec. The car was put on the rack, they checked for drain plug issues, pulled the pressure relief vents in the trunk (they were fine), etc. They requested that I bring the car back when a regional support guy came in for a monthly visit. I did that as well and in short the end result was the same...he smelled the exhaust while driving it, but said everything was up to spec.In the end, the dealership did everything (and more) that I asked of them, just no solution.
DIY Approach #1 -
Some of you may have seen another 4th gen GS owner documented solving the rotten egg smell issue by sealing the two main pressure relief vents in the truck. With the exhaust tips tucked under the bumper, it made sense to me that those vents could be an issue. I ended up duct taping them up completely, re-installing them and then taping them again to be sure. I went as far as to get in the trunk at night with my wife pointing a spot light up under the car to see if any light came. That resulted in some more taping. I was happy with my work, went on a drive the next morning and came back frustrated. For me the smell, as far a I could tell, was exactly the same. Broken, but not defeated I kept thinking about next steps.
DIY Approach #2 -
One cold day I was watching the morning exhaust smoke (condensation) blowing around behind the trunk and it made me think the exhaust may be coming in higher than I thought. I took out the truck lid liner and was kind of shocked to find the back side of it was very dirty with signs of moisture lines through the dust. Clearly dust and light moisture were coming the trunk behind the taillights / trim. Next step was to remove the taillights and when I did I saw the trunk lid is made up of two pieces of steel that are spot welded together. In between those spot welds there is nothing keeping air / moisture out of the trunk which is why the truck liner was so dirty. I went ahead and used clear silicone caulk to fill the seam and used the spotlight technique to make sure I didn't miss anything. The next day I drove the car and the smell was essentially gone. I still get a slight smell if I hammer it on the interstate with the windows open. Windows open must create some type of suction effect? I know my caulking work did not seal the back of the truck completely because there are some slight gaps around the trunk latch that go behind the bumper that I couldn't do anything about.
Not surprisingly, with the truck lid caulked and the pressure release vents sealed/taped, it was very hard to close the doors without slamming them so I took off the vent tape and was pleased to find the smell was still not there. I rarely have anything good to contribute to the forum, but thought this was worth posting in case there is anyone else out there that hates the egg smell. I took some pics when I was caulking everything. I'll find them and post soon.
