I just purchased a 2008 IS250 AWD and after three weeks the dashboard started looking like a Christmas tree with all manner of warning lights. I took it back to the used car dealer and informed them of the 0430 codes along with the check VSC warning. Dealer wants to get out with the least cost no doubt and is proposing replacing the cats with universal units welded into the existing pipes. It looks like the previous owner removed the secondary cats and welded in a straight pipe. So I am not sure what the stock system is supposed to look like. Just how many cats and resonators should there be? Can any and all be replaced by universals and not suffer an untimely death?

The dealer is also saying they are keeping the old O2 sensors because the error is specifically regarding the cats. The car has 109,000 miles on it. Seems to me they are cutting corners not replacing the sensors along with the cats. Comments? Opinions?

 

firstly, did he really straight pipe the downpipe (where the cat converter is)? seems like it would be illegal for a dealership to sell a car that will/does not pass smog checks.

you keep saying "cats" but a car only has 1 "cat" which is the catalytic converter which is attached on a downpipe from the headers. do you mean resonators/mufflers?



from the catback for AWD, each midpipe has 1 resonator and the axelback has 1 muffer near each exhaust tip. so 4 in total, every pipe has a muffler.

how much are they trying to charge you?

if it is more than $200 then youre better off buying a used stock catback and replacing the straight pipe. but in my experience, straight piping an exhaust shouldnt cause any trouble codes as its from the cat converter and back. which mean emissions has not changed.

as for keeping the o2 sensors, thats perfectly fine. that was never removed or changed so it shouldnt matter and its a OEM toyota part so... no need to change.

 

There lies my problem. I am not familiar enough to say what stock should look like. The mechanic I took the car to for inspection also did not know positively what should have been in place where the patch was. The section that was replaced is about 18 inches long and starts where the pipe levels out and extends to just before what I call the main cat midway under the car. Is that actually a resonator? There is also no flex pipe currently. Should there be one between the header and the exhaust? My mechanic thought the section that was replaced may have had a "pup cat" or some kind of pre-cat before the main. For the last three weeks I have had no issues since purchase. It was only the last couple of days that all these errors started appearing. I have been running premium 91 octane fuels. But the first tank-full was whatever the dealer had pumped.
The dealer is proposing using universal units to replace the cats. Of what brand or quality I am still trying to get answered. But they want me to split the cost of $1,500 for two. If they get the cheapest parts they can find I cannot see the cost being more than $300 and the rest is labor. The retailer they are purchasing from carries Walker or Bosal brands. I am not sure how much each uses stainless components, but they only carry a 3-year warranty. For right now, I am cash poor after the purchase and would just like to get it back on the road. I will probably replace the whole exhaust down the road, but cannot swing the expense right now.

 

Just google image the stock exhaust.

Lexus awd: Engine > headers > downpipe (attached with the cat converter) > 2 mid pipes (each with their own resonators) > 2 axels (each with their own muffler)

the o2 sensor should be inserted somewhere after the cat converter, I'm guessing in each mid pipe but I am not sure for lexus 2is awd. In a RWD the o2 sensor is at the beginning of the mid pipe


i think you're better off buying a new exhaust system. $750 is too much just to weld in resonators. honestly, resonators and mufflers have nothing to do with check engine lights. It's just for a louder exhaust sound. Everything that is coming through the exhaust is left over crap that the engine produced so if you have errors popping up, it's a different matter.

on the other hand, if the cat was removed, it is illegal to drive because of emission laws. Then you just need a new downpipe with a cat converter that meets emission laws.

 

If you could take some pictures of the full exhaust, it would help pinpoint what is changed.

 

Image to factory 2nd gen Lexus IS exhaust :

https://www.clublexus.com/forums/att..._is_250_8w.jpg

You can clearly see the secondary cats in the midpipe. The primaries are tucked somewhat into the engine bay as part of the factory headers. You cannot see them here. Most of the black plastic under panels seen here are on JDM model only.

I assume the previous owner had the secondary cats removed. While down there, it's in your best interest to have them put in new secondary O2 sensors. They can purchased for $60 a piece...Denso brand.

 

The dealer is replacing the primary cat on the driver's side. According to your picture the sections replaced did not have any cats. So my mechanic was just guessing that the replaced pipe was something to begin with.