Tabaka

iTrader: (8)

Cabin smells like sulfur and rotton eggs after 45 minutes of driving. Did some research and have concluded that my catalytic convertors have probably gone bad. Currently, the car only has aftermarket TopSpeed Pro1 axle back mufflers with 21 year old factory exhaust in front of it. Looking for input on the next few steps to get everything back to normal. Rarely drive the car because the smell is too strong, which sticks to my skin and clothes. Notice I get headaches which leads to dizziness as well. The cabin gets super hot (yes, I know our cabin gets warm but this is extreme). Since this is a '95, and I'm unsure which cats went bad, think it's a better option to replace everything. Here's my issues which will hopefully get me some clarity to make a good decision.

The car is a 1995, which has two (x2) catalytic convertors.
If both cats are replaced, I will need the entire header/exhaust manifold and mid-pipe.

Unable to post links from external sites per the forum rules, so I'll list my findings from PartsGeek below.
1992-1995 Lexus SC300 Catalytic Converter - Front - Bosal 099-123: $236.33
1992-1995 Lexus SC300 Catalytic Converter - Rear - DEC LX84615A: $210.33
No idea why their marketing department feels like adding thirty three cents to the cost. Nothing psychologically tells me to buy something with an additional .33 cents afterwards.
I have zero Check engine lights or codes, but have nearly 175k miles at this point. Think it's best practice to replace all three oxygen sensors? If so, the cost is roughly $25.00 each for universal Denso branded o2's. That's an additional $75.00.

Total cost, roughly $520, plus shipping, plus gaskets, etc... lets round it all up to $550.00. Lot of dough for third-party "OEM" parts IMO.

Can get aftermarket headers and mid-pipe from OBX for $383.00 + $20 shipping. However, this will remove all of my cats which leads to problems with emissions or worse, the law. The $550.00 is more than I want to pay, but will provide a healthy vehicle that runs decently. This is just one of a dozens of problems, but probably the single issue that keeps me from driving the car more than twice a month. Can't describe the smell other than it's disgusting and probably very bad for humans.

Am I missing other options?

CatManD3W

iTrader: (18)

Eliminate 2nd cat.....cut it out and weld it straight pieces of pipe.....and replace first with a high flow cat...

Or go have a shop build a custom catback setup.....you should be able to get a custom one made for the $550 you stated above

freakness

Dude,

A rotten egg smell is usually associated with unburned gas in the exhaust. One or more of your fuel injectors is possibly not firing (or dripping fuel) or a spark plug isn't sparking. You should test and verify full operation of your ignition and fueling system before doing anything about the catalytic converters.




.

TXMAG

iTrader: (1)

This is the option I'd go with. Should be the most cost effective one as well.

I tend to stay away from inexpensive aftermarket headers as I've had WAY to many issues over the years with poor fitment, broken welds, and warped flanges that never seal.

Tabaka

iTrader: (8)

Interesting. As I have limited access to automotive equipment, would have to rely on a certified mechanic to fully test the entire system. Sounds great in theory, but the vehicle has a huge list of issues. It's like going to the dentist for a tooth ache, knowing you have about seven or eight cavities lol.

INTIMAZY

iTrader: (5)

If you have a rotten egg smell now, it will only be worse if you did a OBX header and mid pipe FYI.
You need a functioning cat to get rid of odors.

That being said, you have a 95 which is OBD1 and is highly highly highly unlikely to get you into trouble with the law. Certain state inspections vary but most states tend to neglect the OBD1 cars now and have become very lax. I'm all for dumping those cats entirely but I wouldn't say I'm a very good influence

If you don't have a check engine light you are less likely to have an injector or ignition issue. Although the OBD1 ECUS tend to forgive misfires more than OBD2 cars, they SHOULD pop a code if a consistent misfire is detected.

freakness

Dude,


It's your car.



Good luck.



.

Ali SC3

iTrader: (10)

By rear do you guys mean that thing on the midpipe? it practically doesn't do anything I thought it was a resonator lol.

I would personally go 1 of 2 ways:

1: If you really need new cats and want the oem style high cell count cats for lowest emission and smell, then just replace the fronts, and poke the rear one through (if it is a cat) just in case its thinking about getting clogged in the future.

2: remove the rear one and weld in a high flow cat in its place (~$70 each for magnaflows plus welding), and then add a second high flow cat in front of it on the same midpipe section (because our cars call for 2 cats if the emissions place is picky)... and spend the rest of the money on a pair of headers with no cats. that way you get headers, and you still have 2 cats for emissions, and everyone is happy, but it wont cut the smell or be as clean emission wise as option 1.
Other benefit to option 2 is you can grab a supra single turbo midpipe ($100 on ebay) and days you want to track etc.. all you have to do is swap the midpipe and bam completely straight through exhaust.


I would also suggest finding out what made the cats go bad though like others have said, they generally do not just go bad on their own usually its a prolonged period of rich mixtures or especially unburnt fuel which will basically burn the catalyst down over time... so if you don't fix the problem, your new cats will suffer the same fate in about 1-2 years, maybe a little more if you drive less.
Definitely replace the front 2 o2 sensors, it could be part of the problem why your mixture was off in the first place, the rear one if you have it (95 usually doesn't unless its cali spec) does not matter whatsoever unless the check engine light is on for it.