theazz

Has anyone performed a replacement of your catalytic converter.
theazz

FlopTop04

I replaced the driver side front cat a couple of years ago at 95,000 miles.

theazz

Did you do it yourself and if so how did it go

Bgw70

Would you mind sharing the reason you think you have a bad catalytic converter?

Do you have a P0420 code?

How many miles?

Is the exhaust stock or modified?

theazz

When I accelerate I get a rotten egg smell i.e. entering the highway. It started about 4 months ago. It only smells when I accelerate. Scanner reads everything is ok. The SC has 97000 miles on it.

Bgw70

I think your cat is fine, how about the easy stuff first...
Tell us the status of the following,
PCV valve
Spark Plugs
Throttle body, has it been cleaned
Mass airflow sensor, has it been cleaned
Fuel filter
Air filter

As for the rotten egg smell, I would get that smell really bad on a hard excelleration, but after I removed the resonator and third cat, it is virtually gone and I still have no check engine lights...

Most will tell you the smell is present on a warm to hot day, top down and you are on the gas, hard.

theazz

Good suggestions
Yes stock exhaust
Everything you mentioned is good . No codes
If I take it to Lexus and had them do a complete diagnostic do you think they could pinpoint the problem.

Bgw70

They could possibly tell you if some of these items are bad...

I would ask you, do you know if any of these items have ever even changed?
If the answer is no, then you should have them all changed.

Also, have you ever had the timing belt changed?
It has nothing to do with the rotten egg smell but will help your engine last longer.

Coleroad

Ydo a live read of your post cat O2 sensors. The purpose of the post cat sensor is for the computer to check the catalytic converter function. A proper functioning cat should give a reading similar to this screenshot. There should be little movement in reading.

Coleroad

Here this will explain why you have the smell. As the fuel burns, the organic sulfur compounds break down into simpler compounds. If the engine is running lean (more air than is needed to burn the fuel), the sulfur is likely to be SO2, or sulfur dioxide. The catalytic converter can change this into SO3 (sulfur trioxide), which then reacts with the catalyst to form sulfates on the catalyst. Over several minutes there is a build up of sulfates. If the engine suddenly starts to run rich (not enough air to burn all the fuel), such as when you stop at a red light, climb a steep hill, or brake hard to slow down, the chemistry changes. Now the sulfates are unstable and they react to form hydrogen sulfide, which is expelled from the exhaust pipe all at once. The high concentration is the reason for the bad smell! This effect is a common problem with new vehicles because the catalyst is working at a very high efficiency. However, as the catalyst gets older, the activity drops. Fortunately for us, one of the first reactions to be affected is the formation of hydrogen sulfide. So as the catalyst gets older, the smell will go away. It should also be noted that many catalysts never smell bad. One reason might be because the vehicle doesn't run lean for much of the time, or perhaps the catalyst has an extra component that reduces the production of hydrogen sulfide.

FlopTop04

I had a CEL with P0420 code. Did it myself at a friends garage. The lift and pneumatic tools made it easy. Used a high quality aftermarket CAT ( $350 ) and gaskets / hardware from Lexus ( think some nuts were $5.69 each! ). CEL cleared and everything is still good 22,000 miles later.

theazz

I called lexus here in St. Louis and they told me if I wasn't getting any codes they doubt they could pinpoint the problem by doing a diagnostic. This all started last summer. Also last summer I had the timing belt replaced, new plugs, new valve cover gaskets, and replaced the master cylinder. car runs fine except for this annoying smell mostly with the windows down. Coleroad your opinion!

Coleroad

Your catalytic converter is fine. My jaguar likes to do this too. It may I stress may be a or both per cat o2's reacting slow. Allowing longer lean then rich conditions.

Coleroad

My jag , it is from to many short trips where it doesn't get warmed up long enough.

Bgw70

Azz, what are you going to do now?
It all started after the work they did last summer and they changed the plugs...did they put the wrong spark plugs in the car (heat range)...
Did they do the other easy things listed above?