LEXSOOS

I hear you , i know that cat's are built to last forever. I also know that it must be something wrong with engine (oil burning, engine running rich for extended period of time, etc..) in order to destroy catalityc conventer. Most likely you're right with cat being replaced as precaution, we'll never find out, but i don't mind having new cat

Why would you suspect that he's running rich?

I would try different gas station for at least two gas tanks and than check on it again

socwrkr

I've actually had it filled at several different gas stations so far due to buying in another state and bringing to this one. I called my mechanic (not lexus) and he said not to worry about it unless i start seeing other problems.. I guess emissions testing will be the determining factor. Just out of curosity, is it true about what Lexus Parts said about having special flanges and not being able to use an aftermarket?

LEXSOOS

Well, i can't help here. I haven't have chance to see Lexus aftermarket cat's. I was looking for cat as well and i think i found one for about $170 or $270 (not sure) but end up not buying, so it's really hard to answer your question. I say DONT MAKE yourself spend money you can save

Vette Boy

The sulfur smell can be result of the cat working too hard (due to be the O2 dying a slow death, the usual symtom is running rich), or it could be the gas. If, after driving a few minutes at a constant speed/throttle position, the car idles rough at a stoplight for 10-30 seconds then smooths out that's another clue (bad O2 is slow to react to changes . O2 sensors at the end of life almost never die a quick death and they need to be very bad before the PCM can detect the sensors are failing.

I agree, this is a good idea, I'd also monitor the fuel mileage the old fashion way (miles between fill up divided by number of gallons added to tank). Bad O2 sensors usual make the car run rich, killing gas mileage and making the exhaust smell like sulfur.

One thing that surprises me is I never see Lexus forum members replacing the O2 sensors as preventive maintanence. New spark plugs, seafoam, change ATF everything but the O2s. Maybe I drove too many GM/Fords, I've found it's a good idea to install new front O2 sensors everything I do the plugs (~75K-100K miles). I never swap out the rear O2s, just wait for the CEL for bad cats and install an old front O2 sensor in the rear (rear O2s only monitor the cats, the output is not used to trim the A/F ratio, that's what the front O2s are for).

DASHOCKER

iTrader: (2)

Are you getting this smell at WOT only? If so, you will have a sulfur smell.

socwrkr

It's hard to tell, i smelled it in the garage yesterday, yet i pulled in after like 4 cars (i live in an apartment) so i'm not sure it was mine afterall as it hasn't done that since, but yes when I stomp on the gas, a few seconds later i can smell that sulfur smell in the car, i never smell it at cruising speeds or slower acceleration, but does not necessarly have to be at WOT either, just hard acceleration. On my way up here from Missouri i got about 430 miles out of a tank of gas and even then i had a few gallons left in the tank when i filled but i was driving on the freeway the whole way with cruise on at about 75mph. The trip computer on the nav estimated it at 26.5mpg average since last fill up when this happened.

DASHOCKER

iTrader: (2)

Sounds normal to me. Ever noticed that smell emitting from cars in front of you that stomp on it? Even my car has a sulfuric smell after WOT and I have no mechanical issues. Better to be safe than sorry. Take it in to the dealer for a diagnostic since your car is under warranty.

socwrkr

I'll do that, thanks for the help!

I do have a warranty (lexus care gold extended warranty), unfortunately, exhaust items (including cats) are not covered.

Lexmex

socwrkr,

Forgive me I don't own a GS series, but everytime I see a question on a cat, I am always curious.

I don't have precats anymore due to a bad batch of gas down here (and don't want anymore issues until I go back to the U.S.), but I have a 3-Way Maganflow High Flow Cat in place of my OEM cat that still passes with here in Mexico City (voluntary testing) without the precats. That High Flow Cat cost me $220 USD installed here (and that is imported cat of course). I would seriously consider it and use one with a .5 inch bigger diameter for a better weld.

You also should have any exhaust gaskets looked at.

BTW, I don't get any CELs related to my cats at all.

socwrkr

Thanks for the input! I will look into all of those options.

Vette Boy

Precats are just for start-up emissions, they're small so they lite off quickly reducing emissions until the main cat warms up and takes over, they aren't needed to pass any emission test (except visual inspection).